Basically as the title suggests, more specifically giant crops are at first immune to structure-destructing bosses' stomps (eg. Bearger, Reanimated Skeleton, Klaus, etc.) when first picked from farmland (can neither block or being destroyed by bosses due to low height of such items; only capable of blocking player/small mob movement), but can be rendered vulnerable to such events when waxed or after experiencing a server reload. Additionally giant crops spawned via console commands are already vulnerable to boss stomps. I think this is quite wrong considering the fact that if you destroyed something via collision, you physically interacted with it, thus mobs're not supposed to destroy something impossible for them to interact with via "collision"
PS: "giant crops" refers to the heavy objects (other heavy objects include chess piece statues, cave-in boulders, suspicious marbles, etc.) harvested from "giant farm plants"
Step 1. grow some giant farm plants; pick the corresponding giant crops
Step 2. summon Bearger/Klaus/Reanimated Skeleton and let them trample on the crops (non-attacking state); the bosses would pass through the crops without breaking them
Step 3. wax such crops/do a rollback to a point when the crops already exist/exit and reenter the game
Step 4. let the same boss mobs trample on said crops; the crops got destroyed