I thought that ADM standard WRX's had open diffs, Foresters a plated rear LSD.

Mine has a 2 way mechanical LSD and an standard open front diff. The Torsen type rear LSD gives excellent traction in the wet, gravel, sand or if one wheel comes off the bitumen, eg rally cars. BUT it wears out tyres, just rolling down a slope and turning the wheel 1/4 turn will stop the car. It tries to push the car in a straight line when locked up. It also only acts as a LSD if both wheels are loaded. When pushing it if one wheel comes off the ground it reverts back to behaving like an open diff. Plated and viscous LSD's don't have this fault. Open or LSD they all have their good and bad points and they can be fussy about having the right oil.