with practice it is quite easy to use the PAPI down to 100ft.
Not disagreeing with anything you have said, but I think this nails the discussion as well as anything.
By "use" the PAPI, you could mean, as I hope you do, monitor it out of the corner of my eye, as one of the many cues and clues available.
Or you could mean make a correction at 150ft to re-establish at 100ft...
I also agree that it was unfortunate that the night element of base training went out of the window (sorry!).