How to reproduce:

1. Make sure you are in a biome where golems leave snow. (I was in a mountains biome)
2. Create an area covered in grass blocks (or dirt) that a golem would not be able to walk out of. (I created a platform in the air using the /fill command)
3. Cover most (but not all) of the area with snowloggable plants. (1-block-high grass and flowers)
4. Create a snow golem in the part without the plants.

As expected, the golem leaves snow in the area without the plants. However, the snow stops generating when the golem begins to walk through the plants. I expected the snow to continue, causing the plants to become snowlogged.