Originally Posted by veganbikes

Yes you may have because 9 speed the pull ratios were the same and didn't change till 10 speed which they diverged and continued that trend because why not.

GRX would be your better bet for using STI levers with wider range cassettes or move to Gevenalle GX levers (assuming mechanical short pull braking) and then you can use an XT or XTR derailleur.