The same is NOT true for all spray lubricants.
The same is true of any sort of spray lubricant, whether it be chain lube, spray grease, whatever. It is all carried by a volitile, usually penetrating "vehicle" solvent. Otherwise, you would have to resort to the now ancient technique of boiling a chain in grease to get it to penetrate into the bushings (DONT try that at home). All of the referred to attributes of this vehicle are commonly found in most good quality lubes.
First we must distinguish between carrier and propellant. Often times spray lubes will be propelled by means of a pressurized hydrocarbon. This is simply a vehicle to propel the fluid from it's holding source. The propellant will have little to do with the penetrating ability of a lube.
A can of spray chain oil or parrafin, like Maxima, uses a propellant to get the stuff out of the can, but the fluid serves as it's own carrier. It needs no further flow vehicle. If the lubricant were raw, as in a motor oil, you can place a drop of the fluid on a plate and it will start to expand it's area. But slowly, due to the viscocity of the fluid.
To even slow things up more, they tackifier added to keep the lube in place starts to set up immediately after hitting the air. In this situation a person can spray a chain link, allowing both sides of the reel to be engulfed in lube...and at this point the lube can actually create an air pocket at the pin/bushing area, as both ends of the reel are clogged up with entering tackifier rich lube.
At this point it is completely normal to see the lube set up before it can penetrate to where it is needed, due to the air pocket not allowing a smoothe enter, and the tackifier setting up.
Lets assume that you have a chain and you lube on link with a drop of motor oil and one with a drop of penetrating solvent carrier dry-film...
The drop of oil will take a considerable amount more time reaching the area it is needed. In fact, you can drop the oil on the link, and then drop the dry-film, and the dry-film will have not only reached the friction area and deposited the lubricant, but it probably has went through to the other side and the excess dripped off before the drop of oil will even reach where it's needed.
Another point to consider, when a spray lube contains a tackifier, it is robbing room for more lube.
The old school method of heating grease up to soak a chain is now and has always been an ignorant method to practice. Yes, I know that it was done for decades, but it is still a method used by those who really don't understand grease and oil.
Anecdotal wisdom also touted this method as "what you should do" at one time...funny how things change. I bet the old school chain soakers were just as hard to convince of a new method, as some are now on chain maintenance and products.
At 4 times a month I count 48 uses.
I use Maxima's Synthetic Chain Guard, as I mentioned earlier. I would probably use half again as much as I currently do if I were not using an O-ring chain, but as it stands, I use about three cans a year, lubing two motorcycles after every ride, or about 4 times a month. So that's what, about 24 uses?
But regardless, it is clear that dry-film goes much further than conventional spray lubes will. (ask ANYONE who uses dry-film)
It is refreshing to see somone actually do some inventigating of a subject. Bob's has lots of good info for those who are a bit curious on the real deal.
Moly lubricant does in fact work that way. But so do the anti-wear additives other than MoS2 found in a good engine oil. Looked at under extreme magnification, the smooth ground surface you see as a bearing journal looks more like a part of the Tetons. MoS2, ZDDP (Zinc Dialkyl Dithiophosphate, the most common, and probably the best of several Zinc and Phosphorus based anti-wear agents), and other "boundary" lubricants work by filling in the irregularities of the surface, flattening it, and coming between the surface being lubed and it's mate in the event that the primary lube source should fail.
And yes, what you describe happening with boundary additives is a fairly good way to explain things to the layman. However, the actions that take place are quite a bit more complex than simply filling in the gaps of the metals surface. Yes, Zinc-D works that way, but most of the other barrier additives work in a slightly different way, even though it may present itself as a simple "filling in of the gaps".
Many barrier additives have no solids at all. They are providing long chain molecules that reside at the oxide layer of the metals surfaces. Due to the dipole electric field, these molecules will attract and adhere themselves to the metals, and they also repel one another, aiding in the lubricity.
When metal violates the fluid film, the shearing that takes place is of the long chain molecules located above the metal surface. When these molecules are sheared, they become sort of a free radical at that point...looking for a home. What happens is that these sheared molecules immediately are looking for another ancor, which they find immediately.
Yes, in motor oils, these barrier additives are placed in the oil as a last line of defence against wear, when the fluid film is violated. BUT it is not an emergency add. It is assumed that the fluid film will fail, thus the addition of the additives. It is NOT an emergency, last ditch, all else fails add.
Most commonly, such agants are added to lubricating oils as an emergency lube, a last line of defense in case the oil film is subjected to such pressure that it is squeezed away. In the case of MoS2, it is so effective as a boundary lube, it can be used as a sole source of lubrication, within limits. But it is more effective when used in combination with a fluid lubricant for two reasons: that being that the presence of an oil provides the primary lube source, as well as a fresh supply of new moly platelets to replenish any that are carried off by wear.
The simple startup and shutdown of a car engine creates the condition that barrier additives are needed.