turbo vs. n/a transmission question (not a strength question)

[matthewb]

Does anyone know why the 944 n/a uses a regular bolt for holding the rear input shaft bearing on but the turbo uses the internal triple square bolt to hold it on? The turbo shaft has a lot more machining inside of it. I wasn't sure if there would be some need for fluid to come up through the shaft and out the back of it. Seems like a lot of extra machining and an odd fastener. There must be some reason.