^^ Lol I think they may have thought that because the foal would still technically be 1/2 Arabian with a 1/4 Paso and 1/4 QH they could still register it as Part-Arab... Unless you were being sarcastic, in which case, ignore this.
It's hard to tell with electronic communication sometimes.
I think no matter what you breed, there's always that off chance that you'll get something different from both parents, although highly more likely in crosses than purebreds! Sometimes two purebreds can produce something spectacularly ugly or strange looking though.
My mare is registered Pinto, but is a bit of a mix. She is 1/2 Paint, 7/16 Arab and 1/16 Thoroughbred. Both her sire and dam were pretty sturdy in build and she ended up much lighter boned than both her sire and her dam.
I think I posted about him before, but friends of my parents brought over a gelding they needed exercised and he was a Percheron/Morgan cross. He was quite unfortunate looking with a sparse, spiky main, thick neck and big head, but you couldn't ask for a more willing or dependable horse. And so smooth, I probably could have carried a glass of water without spilling a drop on him.