The last 3 miles is an interesting phenomenon. I don't think it is unique to MWMT. I have experienced the same on many, perhaps every, a yo-yo day hike I can remember. Most recently on the AR. How can this stretch be so beautiful on the way up and the cause of so much suffering on the way down? No way are you more pumped for the hike any time as you are in those first 3 miles, or as tired and ready for the B&B* as on the last.
It could be an E ride and still be agonizing.
My strategy at this point is to descend at the same rate I came up, rest, and take in everything I might have missed the first time around. Its not often you get such a second chance late in the game.
*Burger & Beer, Bed & Breakfeast, Bed & _______, Benedectine & Brandy, Brioche & Bordeaux . . .