I'm not sure I agree that most dogs are in rescue for behavioural reasons/anything the dog has actually done; most seem to be there due to human failing/abandonment. I follow quite a few of the pound pullers; there seem to be a lot of abandoned bitches having been used for breeding (as is the case with our dog we adopted), dogs taken to vets to be pts, dogs left behind when the owners move out etc.
I have seen pounds pts when a dog has bitten rather than release to rescue.
The fact is any dog-whether you get from puppy or rescue-has the capacity to bite, regardless of history. As a kid, we had a cocker spaniel that routinely would bite me unprovoked (literally would walk up and bite me!) and that had been bought from a breeder and loved/treated well from birth.
I suppose it depends on expectations, too, we expected there to be some behavioural issues when we adopted due to the history. In reality, we have had a couple of toileting accidents (completely understandable), separation anxiety (now settled down almost completely-and understandable, we are the only kindness she has known) and dog reactivity (not aggressive-no barking, growling, snarling-she pulls to get away as quickly as she can, again understandable).
The most upsetting "issue" was watching her trying to nurse teddies on arrival-probably because her pups were taken away too soon after the last litter. She repeated this after her spay as well. But thats hardly her fault and with kindness and encouragement she is doing well now.
If someone could have shown me these in advance I would 100% still have adopted her.
She is incredibly loving and seeks out cuddles; intelligent enough to learn new skills, well behaved in the home, great on the lead, no resource guarding whatsoever and has never ever growled.
I recognise we have been very lucky with her, but I have seen others adopted and similarly just need a decent owner to love them.
With puppies, any breed is pretty much manageable for anyone-until they start getting bigger and I don't think some people think beyond puppy stage. I am thinking of bigger breeds, like Cane corsos/german shepherds/belgian mailnois-all beautiful breeds but need proper care. When they become adults, I think a lot of people realise they cannot /won't give that and they end up in rescue.
If people adopt an adult rescue, at least you can see how big the dog is and understand what kind of care the dog will need during adult life.