Thrall pots have been bugged or broken essentially since they came out but I think at the beginning of 3.0 they tried to implement a fix where thralls would stop taking out food until they slot cap. The fix failed and instead made thralls pots unusable (they used to have a list in them that shows you what thralls are connected to it). It’s been this way for over a year now… don’t hold your breath.
Like the sated bug, which has also been around since early 3.0, it has been determined that this issue is the lowest of the low priority wise.
When bugs have been around this long its best to just accept them as unintended features of the game. For example, for several years Lian has been bugged to always do 100% full combos (unless staggered) with a 1h mace. They’re never going to fix it so might as abuse it.