My dog was about 9 months when we got her. She looked like a collie, and had the sweetest nature, if a little quiet at the time (She gets like that when she’s scared). The vets said there were no signs of abuse, thank goodness, but what we have later come to suspect is that she was simply neglected. At 9 months old, she wasn’t house or leash-trained and I half-joked at the time that it was as if she’d never seen another dog, person, car, etc. I now think that may have been true.
We got her as a pet/friend for my then 7 year old, who had 2 older sibs who would soon be leaving for college. Although he loves her, he didn’t get a “dog” dog — she doesn’t play. Throw a ball and she’ll maybe go after it to see what it’s all about, but that’s it. Give her a pull toy and she won’t. Run around and she doesn’t run and follow. etc. She barely lets us hug her. It’s all on her terms, and that’s fine.
We also found out (through a DNA test) that she has a lot of breeds in her that we probably wouldn’t have taken on in a rescue dog, despite looking like a cross between a collie and a husky. So I would add that even if you rescue a puppy with no history of neglect or abuse, you still often don’t know what you’re getting.