For offroad soft springs can work great in conjunction with high oil levels and the correct valving.  It's just a different approach.  If you have soft springs, low oil level and soft valving then you may have problems.  I know Dwight runs near max oil level as I have read some of his other posts.

For Mx you often go more the opposite way

Everyone I've come across for offroad has always settled on stiffer springs, more open valving, and a slightly lower oil height.  Gotta keep that midrange nice and open and plush for the unexpected out in the fast stuff.

Whatever guys.  I didn't develop the formula I only stated what I have been schooled by prominate tuners for many years.  If you want to turn follow my formula. If you want to go through whoops then go with yours.  I try to spring for turning and valve for whoops and bumps. To say I am wrong with my formula is your opinion only. You have never seen someone crash using my formula. Why you would say that is beyond me.  Just say you disagree.  Both ends have to work together. You can't have one end wrong and the other right.  If stiffer springs give you the proper sag numbers then great.  If you need lighter then you need lighter to get the right sag numbers.  I have only gone stiffer on springs on my XR250s.  Every other bike I have race used stock springs until recent years when I found that springs were too stiff.  Most modern bikes have too light a rear shock spring to get the correct sag numbers.  So they end up running too much preload trying to balance with too stiff a fork spring.