The fact that they already ruled him out more than 24 hours before the game seems telling. Not even doubtful or questionable, straight up "OUT". Really doesn't sound like someone who will even be available for Game 5.
I still think ultimately, he either comes back for a potential Game 6 if it gets there + there's some desperation from Boston at that point, or simply he comes back Game 1 of the Finals which is still 10 days away.
I won't lie though, I'm starting to also fear they haven't been honest this whole time and KP's injury is really severe, to the point where he might not even be available at the beginning of the Finals. It's not like the Celtics medical staff is perfect (look at the Timelord, Isaiah Thomas, etc. situations)