Forge Version: 1.16.5 - 36.2.0
Mod Version: SnowRealMagic-2.5.8 & Kiwi-3.5.2
Can you reproduce this issue with relevant mods only?: Yes

Snow will not build up on the bottom variants of all vanilla slabs. Even when I only put this mod + Kiwi (as dependency) in my mods folder it would still not work. Even though their snow covered variants are loaded because I can see them in my creative tab and am able to place them.

• Natural snow downfalls in snowy biome will not cover bottom slabs in snow.
• Trying to forcefully cover them by using a snow layer also does not work.
• Stairs, fences, fencegates and walls all work fine for me. (natural snow buildup- & snow layer placement covers them in snow).

Is this yet to be inplemented or is this a bug?

For now falling back to version 2.5.6 of SnowRealMagic seems to have fixed this problem for me.