G.B.
When we took the foster parent classes we had a section on similar situations...really, just read on....lol.
When a child is taken from their home there is no telling the exact reasons, even if the child welfare worker is being honest, they are not going to know everything or willing to tell everything.
For example:
One child may freak out in the bathroom each and every time you even say the word. You have no idea what has happened to that child in that room. They could have had to sit in freezing water, hot water, held under the water, forced to do any number of things.
The same with this dog. No telling what the previous owners did to this dog while he was in their care. I would just try and find a way he is comfortable eating and go with it, even if it is off the floor. He may have been punished if he ate food at the wrong time, there are so many possibilities.