True, it can be done in situ BUT it is difficult to realign the banjo bolt and copper washers upon installation because of the angles working at. I find it easier to remove the pipe attached to the alt when replacing/ removing alt and reattach a new pipe before dropping alt back into place. Obviously I don't remove the alt when just replacing the pipe, but it is difficult to re attach.
Defenders are also easier to do than D2's

JC