Yes, and I think that's why May didn't talk to Foster about it before (allegedly) going to agree it with the EU.
My assumption is that she thought if she could get it all agreed it might just go through. Foster could kick up, but it would be too late, the rest of the UK could kick up, but it would be too late. The EU would have agreed to move on to the next phase (which is what the British government want) and "the details could be sorted out later".
Obviously had she talked to anyone at all she would have discovered pdq that the shit was about to hit the fan 
Naivity, stupidity, or deliberately calculated to cause the maximum confusion? I don't know.