I'll never understand how people can confuse a race that transplanted existing populations a few hundred years ago with a race that seeded the evolution of entire biospheres four billion years ago. Why do people assume everything in the past happened at the same time?
I guess the conceit of them going into hibernation makes a little more sense, except there's no reason the two should be associated at all, besides the metatextual reason that they're both excuses for humanoid aliens.
I can sympathize with your frustration here. According to Memory Alpha, Ronald D. Moore said back in the 1990s that he had considered but did not end up using the interpretation that the progenitor humanoids were the Preservers. He noted, however that
but this could be them and be internally consistent
There's no reasonable way that it could be true in the novelverse given what your novel The Buried Age
says that the Manraloth did, though, can there?