Rivet gun - reduced scatter due to cut off; not necessarily so. The 146 landing performance was not predicated on the performance at LCY, but was determined from flight-testing on steep approaches elsewhere.
Extracts from a BAe safety presentation used some of the data in the CAA report and indicates that 5% of the touchdowns at LCY were beyond the fixed distance markings (only just beyond). The overall distribution was skewed with the median about 800 ft in from the threshold.
The lights inset into the runway are fixed markers to aid the crew; however, they should be used as you suggest.
JT your points reflect commonly held views, which in my experience are not necessarily true. Increase in judgement / workload / skill; yes, there is less margin for error in commencing the flare, but the mechanics of flaring and judging the touchdown are basically the same as for any landing; height rate vs height. Pilots quickly adapt (3 landings) and retain the ‘skill’ in a similar manner to remembering the change in approach and flare during an engine out / glide forced landing.
At some time during the CAA trials (by chance), the FAA filmed landings at LCY as part of a research project on aircraft gear loading; they held the view that steep approaches would increase the average load, presumably due to a spread of pilot judgement. To their surprise, there was no such correlation, nor do I recall any 146 suffering gear problems, but one wouldn’t with such a robust design would they.
The skill in the flight testing is to flare as late as possible and stay within the test conditions of not more than 6 ft/sec (and not less, which performance engineer requires).