Either way, there was certainly something sketchy going on with this poor guy. I had the impression that he was a bit of an exception to shelter norms. Why else would he be held with his siblings for so long without being open for adoption? Why would he still be matted, four weeks after being admitted to the shelter?! Other shelters I know shave (or clip really closely) matted dogs, even if they don't want the expense of properly grooming them.
Luckily, his neutering cut no longer looks so fresh. I think all his licking had kept it from healing properly for several days. Thank you e-collar!
He's quite an idiot, though. He is totally incapable of doing his business outside when his cone is on. I resisted taking it off of him for the good part of the day yesterday, assuming (how silly of me!) that once he had to go badly enough, he'd potty with the cone on. But no. He held it for an incredibly long time, until I became genuinely concerned for his health if he'd held it for any longer and so I gave in, taking his cone off. (He pottied as soon as he got to his spot after that, and I could tell he was so relieved not to have to hold it any longer. Gah!)
He also can't figure out a food puzzle for the life of him, even with his cone off. We have a tricky treat ball other fosters of ours loved, and we filled it up with food like we did for them, and he never figured out to roll it for food, even when he accidentally rolled it a couple times and got food out. He just stared at it in puzzlement, then wandered off.

We're hoping he'll show some unsuspected intelligence once he's cone-free. Sigh. What an easy-going dog, though, in spite of all his hardships!