My two came from the adoption section in Pets at Home, and were probably around four months old at the time. Both had clearly been handled before, but I suspect they were there because Blitzen was a biter. He's not generally okay with being handled, but he is much better now than he was. Comet's fine with handling so I suspect Blitzen's issues are personality based and not from being wrongly handled, but of course I can't be sure. That said it took a lot of work to get him this far and he still refuses to let me groom him 98% of the time, which is fun when he has such a beautiful full sheltie coat.
He'd likely have the same issues in a rescue, except I'd probably have found out he was a biter before I brought him home. I don't care, but it would be a dealbreaker for some, I think, and he'd risk being split from Comet because Comet's so much more comfortable with handling. They get along well with each other, it would have been a shame.
But if I'd been a first time owner, or a parent with kids, he wouldn't maybe have fared so well. He is a downright nuisance don't get me wrong, but a hilarious one and that's who he is. Shelter piggies are going to have some obvious personality traits before you bring them home, it can be less of a shock as to who you end up with.