The FCTM gives a pretty accurate description and I don't think it's necessary to explain it any differently to the trainee.
I agree 100%.
At the end of the day this bit of the flight is different to most other parts of the flight in that it is 100% visual. It’s nothing but flying a plane. I suspect that many people who have difficulty landing consistently are weaving in some other form of perception, ie rad alt call outs or rad alt heights or something, and that will only work in relatively benign conditions. The FCTM uses the runway end as a cue because there will always be a runway end on each landing, there may not be a rad alt call or there may be no time to check a rad alt read out. The cue to initiate the flare should come from visual peripheral perceptions and it might be at 30 ft or it might be at 15tt. If new FO’s can sneak through training with a rote technique based on something other than visual perceptions outside the aircraft then when they get to a more challenging landing condition ( gusty crosswinds etc) they won’t have the habit of looking out the window to the far end sufficiently embedded to do a nice job of it.