why does outback xt ride rougher than the standard?

My guess is the turbocharged car has a suspension that is firmer for better handling. The Subaru site really does not say anything about the suspension. You might be feeling the difference between 17" and 18" tires.

Nope! The suspension is unfortunately identical, with huge body roll and poor yaw. I compared both; nothing inexpensive can be done to remediate this comfort-at-handling- expense Toyoburu iteration yet. Maybe there'll be a mid-cycle (2023) upgrade? Doubt it....

Yes, you may be feeling the tire sidewall compliance delta. The OE 17" tires are garbage. Upgrade to 225/60HR17 at the first opportunity. The 18" are ok, also benefit nicely to a lower 225/55H/VR18 profile. Handles only SLIGHTLY better, as there's no fatter rear swaybar available to reduce understeer nor reduce body roll...yet.