Made the same starting character and gave him 275 of a skill using a mod before and after patch. The only difference I can see is that after the patch having a skill over your limit is more heavily penalized.
Before: skill at 275, limit 220 ---> learning rate 2.8 due to -6 penalty for skill level over learning limit (5 focus points, 8 attribute)
After: skill at 275, limit 220 ---> learning rate 0 due to -14 penalty
Other than that all learning rate and EXP requirements seem identical. It is possible that the change affects how much skill EXP actions provide based on skill lvl (i.e. how much bow skill EXP do you get from doing 100 bow dmg), I have not tested that. But I believe those should be constant, not in any way dependent on skill lvl.
Interesting. Tested it for charm gain in the tutorial. 0 -> 48 pre-update. 0 -> 52 after update. (Green zone is a mere 10)
Since I get one instance of exp big enough to make me jump to 52, that instance is technically using the multiplier when the charm was at 0 meaning it was in the green zone. Normally, the red cap would be 18 if I get small charm xp gains one at a time, not a whopping 48 or 52.
Taking what you found out and that into consideration, I think that we can conclude that the new formula gives more XP beneath the green zone and less when you go over it.
In a way, that's actually pretty damn good because you can control your stats better. Growing certain stats unintentionally past the sweet zone hinders the growth rate of the skills that matter to you. Wish the developers were more clear in their patch notes though.