It is very realistic!
I just did KPBI to UAAA (12:36) the other day and landed with 8K onboard. (.88-.90 the whole way) and we are doing UAAA-KTEB (12:02) tomorrow (.88 because the burn is cheaper/very compatible to the same fuel burn as our previous G450).
Dont listen to the guys who have never flown the plane.