Considering they were ghosts who freely traipsed around the moon and multiple worlds and have been around for 12,000 years, I don't think there's anything they didn't know. Emet-Selch knew about Vrtra's "secret" underwater treasure hoard after all.
I think the use of the Ancient script is interesting and there's a connection somewhere, but I don't for a second believe that they are Ancients themselves. WE are descendants of the Ancients and are moving forward instead of trying to reclaim the past and that whole story beat has been done already so I doubt they'd retread it.
