The transmission in my teardown thread is from a Range Rover L322 rather than from an BMW E53, and the selector levers for the two vehicles are on opposite sides of the casing. On the Range Rover the lever is on the LH side of the transmission on the opposite side to the inhibitor switch and it therefore has a long selector shaft which extends across the full width of the casing. It only has a single roll pin to connect the selector shaft to the rooster comb and the moving part of the inhibitor switch. The use of a plastic spacer (highlighted in yellow, below) means that the shaft cannot move axially and requires no further retention.
For the E53, where the selector lever is on the LH side of the vehicle, only a short selector shaft is needed, and an additional pin is used to locate the selector shaft axially (exactly as you stated).
I cant see why the selector lever needs to be removed from the end of the shaft, just so it can be withdrawn far enough for the inhibitor switch to be extracted, either.
Phil