If you place Grass Blocks onto a single snow layer it will destroy the snow layer (normal) but instead of placing a Grass Block it places a Snowy Grass Block as if there is snow on top of it.
Placing any block on top of the Snowy Grass Block converts it back into a grass block.

https://imgur.com/a/okYpF1b

Also, any snow layer more than 1 or snow block removes the the grass on the block below it, not sure if this is a feature or another bug but I noticed this as well