I know that this may vary from store to store. I know that assorted africans are usually hybrids or of lesser quality. Are the discus hybrids or a lesser quality if you buy them from a dealer that labels some as asst.?
Few retailers buy quality discus from breeders for resale. Most end up with culls no one else wants. They order them sight unseen from places that put many fish from different places together in holding tanks. The ones that manage to survive against the odds, end up in your dealers tanks. Certainly not the way you want to build up your discus stock.
A hybrid doesn't mean a low quality fish. What we know as domestic discus have been crossed and recrossed many times to produce distinctive characteristics. A low quality fish has poor shape, large eyes, poor fins etc., a cull. In theory, it's important for the sake of the strain that such genes be removed from the gene pool. In reality, people who buy such fish rarely keep them alive long enough to breed them. I think it's important that we distinguish between the two.
Assorted does not mean lesser quality. It means the wholesaler is shipping you an order with various strains, instead of just 1 strain of discus.
Most LFS don't need a box of 1 strain of discus. So they order an assorted box to get a mixture of strains(various colors)that the wholesaler has available. It's like getting a box of assorted chocolates. The problem with an assorted box of discus is you might get strains that you don't want. Plus the different strains might come from different breeders which could lead to disease problems.
I guess it depends on where you are. Most of the 'assorted discus' around here are low quailty ... bad colors or patterns, bad shape, even mixed strains. True I've seen two heckels once in an assorted tank, but usually it seems it's fish that should have been culled but the breeder wanted more money.