Great sex is between the ears, but, if a male bodied person is undergoing the process of becoming female, hmmm logic would seem to suggest the process is responsible. In due time, transitioning means replacing the part. Eventually there simply won't be a penis present.
But from what little I know (which is very little) they don't remove the on button, they just wire it up to a input device (I hope that analogy makes some sense).
Eventually, it all becomes 'what exactly is it that makes the person reach the point where they groan out their OMG moment?'. Because given enough time, won't it be two girls having sex? If you are female and 'he' is becoming female, then you will both be needing the strap on.