Snow layers can now be placed on upper, closed trap doors. Opening the trap door breaks the snow layer, but this does not drop a snowball. Snow layers can be broken by a piston and drop snowballs. The behaviour is inconsistent with other blocks

Test: 1) Place an upper trap door and ensure it is closed. 2) Place one or more snow layers on top of the trap door. 3) Open the trap door.

Expected result: The snow layer(s) should break and drop one or more snowball item. This is similar to the behaviour of all other blocks that require support, e.g. redstone dust, repeaters, lanterns, scaffolding, etc.

Observed result: The snow layer(s) break and no items are dropped

Note1: placing more than 8 snow layers, causes the first block to be destroyed and any subsequent layers above that to fall, break on the open trap door and drop a snowball.

Note2: Blocks such as glow lichen and sculk veins are destroyed without dropping an item, when their supporting trap door is opened. However, these blocks do not drop items when pushed by a piston, so this is expected behaviour.