I don’t know, it looks like you’re doing everything according to the other topic.
I found several other topics on this same type of thing but I can’t fine the one quote Elliot in your OP.
At this point I think you should open up a new support ticket https://support.advancedcustomfields.com/new-ticket/ they might be able to help you more than I am. I don’t see any reason why the terms should not be saved correctly.
