mushroom stem (and all-sided stem) are unique blocks, which don't drop anything and which don't stack with other shroom variants when block-picked.
They also get mapped to the same block when placed, and there's no distinction between red mushroom stem and brown mushroom stem.
Now, blocks do not respond to silk touch unless specifically opted into. Since this always involves custom drops in one way or another, it's easy enough to figure out which blocks need to be marked for silk touch - anything that overrides getDrops, getDropsForCompatibleTool or getSilkTouchDrops is a block which _might_ need to be flagged. Using these criteria to reduce the number of blocks needing to be checked, I was able to manually invert the behaviour as needed.
This fixes reoccurring bugs with blocks erroneously dropping themselves whenever new blocks are added and someone forgot to set that flag, granting players access to internal blocks with strange behaviour.
