The outer tire diameter for the 5th gen Legacy family is about the same; They all come with the same donut spare.
I will say this outer diameter is LESS than stock diameter. The recommendation is to not drive fast, and don't drive far. Last time I needed the donut spare, I lowered the air pressure in the tires to better match the spare's OD. Drove slow and less than two miles to a tire shop.
I have an 07 OB; that OD is greater than our spares. Go figure since our gen stepped up a size for sidewall aspect ratio. Do not know if the current OB use the same donut as the Legacy.