The Nomads that destroyed Sol are a different kind of Nomads to the ones that reside in Sirius.
The Sirius Nomads woke up at 350A.S., which is over 400 years after Sol was destroyed. Plus the Sirius Nomads have had no contact or communication with any of the non-Sirius Nomads.
Different race of beings, and no one survived Sol to tell the tale, so the Sleeper Ships don't know what they left behind.