It is my recollection that the reason to not can cooked and mashed pumpkin (or other squash) is the density which risks not having everything reach the optimum temperature to kill bacteria. Leaving it in chunks will apparently allow all the produce to reach the correct temp.
When I helped out with judging at my community fair, we used the Ball Blue Book as a reference for proper timing/pressure/method. Sadly, if a person didn't process per the Ball Book, their entry was disqualified. I felt horrible one year when an absolutely gorgeous quart of canned pears with almonds had to be disqualified because the woman processed it 5 minutes less than advised. It really would have won Best of Show otherwise, and I know the woman was sorely disappointed to not get any sort of ribbon for her hard work.
