Since 1.16, creepers damage players and other mobs normally when they are on snow layers or carpet. In 1.15 and earlier, they would only do half a heart instead.
This seems like a bug, since MC-145 was closed as WAI, with Grum confirming that the snow absorbs the explosion damage.
Comments 3
This got fixed by MC-178947.
It's reporting the opposite, how MC-145 was WAI no longer being the case.
I suspect that WAI was more of a "we don't care about it" behavior though, and not "we will keep this in the game".
Can confirm, but I fully expect this to be working as intended now.