They're still considered Kuro's kin. The variation in sub-species of lower dragons or 'wyrms' are implied to be due to inbreeding or combination from experiments of Potimas on a true dragon. In fact most monsters are probably either his creation, or descended from hybrids resulting from his experiments.
Potimas engaged in those experiments to investigate how MA energy and conjuring worked. Even if they are 'imitations', that doesn't mean he didn't make something that worked like the real thing. They use skills and stats, but clearly they have a lot in common with true dragons. For example, some of them can transform into human form, and that is not a skill. They don't know how to do real conjuring like true dragons, so that is a problem for them when the System is gone. But they're still related to dragons, and they have the potential. The distinction isn't very important....for example, I don't think there's any strong argument that Sophia isn't a proper recreation of the ancient vampire race that existed on this planet before the System. Yet she also relies on said System for pretty much everything.
And that makes sense because the System is more like a cheat menu than something that allows things that are not possible, except for evolution. If Kumoko was born an Arachne, and lived long enough, on the order of thousands of years, to grow her energy and learn how to using conjuring magic, she could maybe become Shiro the goddess on her own. It just would never happen because she'd never live that long, plus she wouldn't have a single 'skill' until she's maybe 90% of the way there. The same goes for dragons, imitation or true ones. Dragons are just advantaged in this respect because they are both near immortal and born with an instinct on how to perform magic.
All this is also a little beside the point. Even if the System dragons found themselves having lost all of said stats and skills, they're still great big lizards, with sharp teeth, giant claws, armor-like scales and human-or-greater intelligence.