(Just to clarify, I mean tall grass as in what used to be called double tall grass, but was renamed to tall grass in Java Edition 1.13.)
Snow layers do not generate in tall grass like they do normal grass. This is likely due to the attempted fix of
- Find a snowy biome. Try using the seed 1410403532.
- Find some tall grass in the snowy biome.
- Notice that, unlike the normal grass, there is no snow layer inside the tall grass.