I could be mistaken, but somewhere I learned that that Train (and maybe Engine as well) are based at Cumberland. If everything goes well, then crews can be turned on continuous time at Wash and Pgh (saving $$$ on expensive hotels). For all we know, the "board was dry" at Cumberland, and there was no alternative other than to hold 30 (7) for 29 (8) at Pgh.
So far as assigning sufficient crews to Cumberland to cover such emergencies, the BLET Local Chairman at Cumberland, will love you for your suggestion Mr. Ohio. But Extra Board assignments come with guaranteed pay and benefits - and that translates into the "secret ingredient" of which Amtrak is perpetually short.