I wasn't accusing YOU of lying, sorry that it may have read as if I was.
I was saying that it happens and IME it's just as often that the owner will be being disparaging of their dog than will be covering up the dog's bad points, if not more so.
Your comments are sadly true of the minority of rescues, I admit. A rescue I know of only last week put not just the good rescues at risk of suspicion and rejection last week, they did it to the unwanted dogs of this land too. Not content with putting an unneutered dog in with another dog and thus causing a nasty fight they then put a dog-aggressive large dog into a foster home straight from the pound...
... a foster home with a tiny Chihuahua.
Both dogs are now dead, the Chi killed and the bigger dog PTS as a result. :( 
So yep, i know it happens. We all went ape, they have closed their wensite and FB appeals page and none of the three main people or their assistants will ever get to work with us rescue volunteers and independent networkers again. We do tend to monitor each other as best we can.
I'm a tensy bit envious of you fostering pups, btw.
If I had room there would be a Staffie or ten here with my boys... :)