Does all wood glue need to be removed from a cement floor to use thinset to seat ceramic tile?
I was mixing thinset on my porch last year and some dropped on the cement.  My son started wiping it up and I said "don't bother" and he was a bit surprised.  Went to the porch a week later with a putty knife and popped the thinset off with a few taps of a hammer on the putty knife.  Moral of the story being thinset kind of binds to concrete but not really.  It "sticks" and if you use some bonding agents it might do a little better than stick.  But it doesn't "bond" to cured concrete.

Another example is in my area a lot of bathrooms were poured concrete over subfloor - about an inch - then thinset and tile.  I have demo'ed 50-100 of these bathrooms.  I just tap a hammer along the tiles like I am beating a drum.  The vibrations will cause the thinset to "unstick" and I can have an average bathroom floor detiled and dethinsetted in 2 hours while leaving the original concrete in almost perfect condition.

So whether you husband is applying the thinset to the concrete or concrete with a little wood glue on top, he should expect the same amount of "stick".  The only way I could see the wood glue interfering is if it were still loose or became loose during the install, and even then this doesn't seem to be a huge obstacle.  Thinset doesn't need to have a permanent bind to the subfloor to perform well.  In fact if it did it may perform worse and crack at certain points.  The important thing is the thinset binding with itself.