Affects snow layers, cobwebs, and possibly some other.

Expected:
Mining a layer of snow with a silk touch pickaxe should drop a snow layer, the same way mining a bookcase with a silk touch pickaxe drops a bookcase and not the raw books.
This is consistent with /loot give @s mine ~ ~ ~ mainhand

Actual:
Mining it manually with a silk touch pickaxe gives nothing.
Using the /loot command will however drop you the snow layer.

Steps to reproduce:

• Run below commands while standing on a snow layer holding the pickaxe with silk touch.

/loot give @s mine ~ ~ ~ mainhand

• Alternatively, stand on the snow layer and just use:

/loot give @s mine ~ ~ ~ minecraft:diamond_pickaxe{Enchantments:[{id:"silk_touch",lvl:1}]}

Try to break the snow layer manually with the same pickaxe. You get nothing.

Suggested fix:

• Either make it consistent that both drop the item, or neither drop the item.
• Additionally, you should take a look at 'required item' + silk touch for various blocks and re-determine if it should or should not drop a block and make it consistent with /loot