I confess I didn't see the play live, but there are a couple of possibilities: 1) hit and run was on on the swing; 2) 'crossing up the defense'.
I have certainly seen numerous occasions where the bunt is put on and then taken off or vice versa.
Yeah, Castillo sort of got screwed twice, first by the old rule and now by the new one. They really have a dilemma on their hands if he continues to play well. Do they really want to pay him for 3 more years to play for the PawSox?