Yes, there were twin turbo Legacies, but I thought they were phased out by the mid 90's when turbo technologies improved. I seem to remember hearing internet rumours about them being a bit unreliable, though; which was another reason for moving to a single turbo solution.
Yea the engine cover doesn't seem stockish on that engine. Could be trying to pull a fast one on someone not local or unaware.
Also, fitting both turbos is a royal PITA in a LHD car. It could be legit, but something is fishy there