After conflicting information on the net I finally purchased el-cheapo endoscope camera and took some snaps of the differential.
Pictures are crap but enough to confirm that the diff is Torsen:
What you see is the helical gear shafts (I also confirmed that by spinning the wheel and observed the shafts spinning).
If it was clutch type it would had clutches, shims and cam mechanism visible instead.
In conclusion at least my JDM GRB STI came with Torsen (and it does not look like it was after market installation as all the bolts and seals are pristine).