Cool thread.
I agree that two hours of minimum cxn time should be considered if you travel from outside the U.S. into PHL and have a domestic cxn. This is especially true for non-U.S. citizens. I travelled recently FRA-PHL-MCO and queues at immigration were atrocious (1:20 waiting time). On your walk from A-arrivials to C (C28 im my case ) or even F you have to pass a security checkpoint which typically is jammed with all the arriving tourists and therefore is slooow (only two lines open). If you have to go to the F gates add another 15 minutes.
Thus, three hours should be a secure choice. You may always relax in the lounge (or in one of those nice rocking chairs).