Villagers with manually set trades won't loose their profession when their work space is broken.

I was playing in 1.14.3 and I was messing around with a village in survival vanilla Minecraft. I changed a villagers profession to a tool smith, decided his trades were bad, and removed his work station. However, this villager didn't loose his profession, nor could I trade with him. I tried to relog, but things were still acting a bit weird. What I mean by not being able to trade is not him being locked out and not having a workstation to replenish his supplies, but the UI would be very buggy and it would show up for a half a second and then just disappear. I went to the other villagers in a creative test world to lock them out and remove their workstations, but the trade UI was still working. Also, I did eventually put the toolsmith's smithing table back, but the UI was still broken. Is this a bug or a feature? Please fix this if it's a bug!