I have never heard this before and would be interested to see a source. I wouldn't find it terribly surprising but I find in my first hand experience there are more dogs that end up in shelters because their owners were moving, couldn't afford them anymore (including for illness), or even died. Some reasons that I see just plain don't make sense, like one dog that was brought in with the reason "doesnt love enough".It is easy to assume that most dogs in resuce etc experence abuse and neglect and is the cause of the behavior wen in actually it is their behavior that landed then in rescue and shelters. Behavioral issue is the nimber one reason why dog are released by owner to shelters in survey after survey.
That said the VAST majority of dogs in shelters around here at least were picked up as strays and never claimed. So the reason of the owner for not finding them is unknown.
You must also consider that the shelter environment is very stressful for a dog, and dogs often develop behavior problems while in the shelter that they didn't have before. This is why most decent no-kill shelters will eventually send a dog to a foster home or to a less stressful rescue environment if they aren't adopted after a certain amount of time in the shelter, also freeing up a spot for another dog.
Anyway 9/10 dogs in the shelters that I work with have no noticeable behavior problems. Most of them are well behaved, though perhaps too energetic for me personally.