Resolved the mystery as to why my KX60 seems so much different than I'd expect:

It's got an internal rotor ignition!
Which would be really nice, if that's what I wanted.
So, can anyone tell me, what do I need to revert this to stock?
Just flywheel and stator? Plug coil? (I think so) CDI? (don't think so).

But I'd like someone who has some experience to ease my mind. I can't find a kit for sale, so I can't say "Oh! that's included".

Barring input from someone who knows, I'm probably going to pick up the whole mess, flywheel, stator, CDI and plug to avoid missing something I need.

I have an answer.
The motoplat ignition uses a different stator, flywheel, and coil than the stock bike. It does not use a CDI, at least not a separate component CDI, it may be incorporated into the coil. It also does not use a woodruff key. It uses the stock kill-switch.
So, to revert a KX60 from motoplat to stock, you'll need:
Flywheel
Stator
CDI
Plug coil
Woodruff key
And assume the hardware to mount this as well, mostly 6mm bolts.

Motoplat's internal flywheel is significantly smaller than the stocker, 88mm vs. 64 mm. I have no idea what kind of mass difference there is, since the scales I have are either too small (jeweler's scale) or too big (bathroom scale) to measure them. They feel about the same. But the motoplat is a solid cylinder, the stocker is more of a hoop. The rotating inertia of a hoop is twice that of a cylinder, assuming both are the same diameter and mass, since the motoplat is not only smaller diameter, it's solid, this probably gives it the advantage of much less than half the inertia allowing the engine to spin much easier.

If anyone is interested, I'm happy to sell this as I no longer need it. It should work on any KX60 or KDX80, possibly works on KX65 and possibly KX500 (like you need any power finders on that). It is not a direct bolt on, there is a adapter plate for the stator and the coil must be mounted somewhere else, it does not fit in the stock location. It has a very long plug wire because of this.
PM me, I take any measurements you need before shipping.