I don't mean to be sceptical, but did you actually see a spigot bearing there? or do you assume that MRT would always fit one just because they are MRT?
New flywheels do not normally come with a bearing.
Most cars (not Subaru) have the bearing in the crankshaft, not the flywheel, so your mechanic may have overlooked it if he's unfamiliar with Subaru.
My Boss had a Nissan Patrol that had no spigot bearing in it from new, same symptoms, Nissan couldn't find the fault in 25,000km. By then the gearbox was rooted.