This could perhaps be illustrated well with a hard boiled egg. If you remove an egg at the 7 minute mark, the internal temperature is still around 100c, and it will continue to cook. To stop it cooking, dunk it in cold water.
Similarly with the pot pie, the filling retains a ton of heat, so it still is cooking for those few minutes, as the heat dissipates. If you left it in the oven five minutes longer (to 'finish') then put it in cold water (like the egg), you would have a pie in a similar, though wetter, condition.
All Google returns is page after page of recipes and posts about Banquet pot pies that have no connection to my input. Google used to be so good at this kind of thing. I know the answer exists somewhere because I found it once a long time ago searching for answers to the same question. Google found it then.