Hi,
the old Republic worlds write-up was always in error on that part. Even the old Terran Hegemony outline from the original Star League Sourcebook did not show Skat as a Terran Hegemony world.
As such, all the Handbooks, Era Report: 2750, and Historical: LoT 1 are correct.
With regards,
Øystein
Precentor Cartographic