Snow layers do not always fall into snowloggable blocks as they should. A simple example is provided here, but it is unknown in what other cases this issue arises.

Demonstration

The attached video demonstrates the simplest situation wherein this issue arises. The custom block has no collision and can be snowlogged. However, upon breaking the full snow layer block the custom block is filled with, the snow layer above does not fall onto the block.

Reproduction

This issue can be observed with any block that can be snowlogged, custom or Vanilla.

The demo video is taken from the behavior pack in the attached world for convenience. This world can be opened (in Minecraft Preview) for inspection or unzipped to access the code associated with such.