.. the Glideslope flies you down into the touchdown zone which is the 1000 foot markers from the end of the runway (which is basically 300m from the threshold), the idea being that is where you touchdown therefore the runway is effectively that much shorter.
Irrelevant .. the LDR is based on overflying the start of the runway at 50ft which makes the 1000ft point the "normal" target.
Whereas on any other approach the idea is you can aim your approach to touchdown right on the numbers therefore having full length available.
Might be OK, physically, for a small aircraft but, for anything of any size, a good way to leave half the aircraft hanging on the fence.
That requirement for adjusting the landing distance by 13% or 300m is in the CASA B727 Perf and operating Handbook
ah, OK. For the exams, you do what the system expects. My time lecturing in the exams was past when they moved to the 727 as the example aircraft.
From a practical point of view, I can see no relevance either to certification or routine operations. CAT 1 is close enough to CAVOK so far as the final flare and touch down is concerned.