When I went to Glitterglam, I agree they did have many breeding cats (about 30 bengals) and I would say not all kittens are displayed on the site. Certainly not true that only the best ones are put up because the kittens vary in 'quality' i.e. some are pet some are show quality. But a lot of the time they (am sure other breeders do too) keep the nicest specimens back for themselves. So it depends. They are also not a hobby breeder-they breed commercially. That is obvious from the size of their cattery. Nothing wrong with that they seem to take good care of their cats and have lots of staff.
As for the marble..they keep marble's there as breeders as they are 'sheeted' marbles and don't look particularly impressive up against a rossetted cat, which is probably what Glitterglam specialize in. My Toby's mom was a lovvely sheeted marble! She had the most gorgeous golden glitter