Perhaps I don't come across as very understanding.

, but I am really. I had a spaniel cross as a child, she in turn had a misalliance, so the pups were mongrels. in those days, pure breds were expensive and there was a market for pet homes for mongrels and crossbreeds. They all had skin diseases that came from one of the grandparents. Not something my parents could have anticipated in post war times. These were both 'mistakes' but in those days there was no means of preventing misalliances or preventing the issue of such. There is now.
Yes, you are quite correct, all recognised breeds stemmed originally from crossing one with another, but these were planned matings in order to create another breed for specific purposes. My own breed was - the Brittany was a cross between a high spirited short tailed hunting spaniel in France and the pointing and retrieving breeds owned by the English Gentry who went on shooting trips over there. The reason was they needed a dog that could hunt in the woods like a spaniel, point like a pointer so guns could get closer in the rough terrain, and retrieve like a retriever back to the owner, but was small enough to live in the home. Designer dogs are just as it says on the tin - crossing all sorts of breed with anything else in order to make money, with no thought of what they will produce nor the diseases that come with the matings. I assumed that this was a repeat mating from what you said about the owner's description of the offspring, and thus also assumed rightly or wrongly that it was a money making exercise. My sincere apologies if I was wrong and I hope you find good forever homes for the pups, and that they live long and healthy lives.