You say that Apple have no incentive to intentionally brick phones, then that Apple could have made sure that the phones didn't brick. Well, call me stupid but when 100,000+ people have unlocked iPhones, I think Apple does kind of have a responsibility in that, they could have tested the new firmware on an unlocked iPhone to see what happened.
Legally they don't owe these users anything, but ethically, this is still 100,000 customers, why not spend, $75,000 on developing a way around bricking the iPhones but relocking instead, as of those customers who then revert back to AT&T, any money lost on developing will be made in Apple's cut of the call charges.
You probably won't agree with me, but see it from that point of view. 100,000 customers (a lot of which are the most passionate Apple customers) is no small deal.