Twist mount is more done to fit larger turbos that dont have subaru style fitment. Different flanges for the exhaust entry and exit. (Or V band) And also larger air inlets like 4" that simply wont fit under the OEM manifold. And sometimes such large turbos that simply wont fit. It also means FMIC needs to be done.

Twist/rotating an OEM turbo probs wouldnt make any meaningful differance, other than the difference from the FMIC.

But when you compare a stock location version of a larger turbo to that same turbo that is twist mounted. Then the twisted one will perform better. Example : a stock location gt30 made with subaru fitment housings and small diameter intake vs a regular gt30. The insides of the turbos are all the same, same wheel sizes etc, but the stock location wobt perform as good. Probably mainly because the stock location turbo has been choked down on the intake with a 65mm intake to fit under the subaru manifold. But the regular version has a 4" inlet.

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