The terse response is fitting for the actor, and although I expect his diction wildly undersells it, this is probably Tim Allen’s way of saying that the ending is heart wrenching.
I also like how Tim Allen’s warning of the ending amounts to “Tough one.”
The fact that the ending was so emotional that Tim Allen felt compelled to see what his co-star thought and then warned him about it means that it must be a doozy.