Mach E Avelli,
At some stage our student may go on to fly in the world of hard knocks. Like where manual landings in 800 metres visibility with a low cloud base and no visible horizon is expected, or else you don't get to keep your job.
So why not teach pilots to look at the ground just ahead of the aeroplane from day one instead of all this exotic theory which won't work if you can't see the horizon or far end of the runway.
I think the point you are missing is that the reason the author developed his technique was to provide a simple framework of instructional steps for a instructor to use to teach a newby how to land. In other words, it was more aimed as an
instructor's tool rather than a
pilot's tool.
In the absence of a clear and consise methodology such as this, it is difficult for an instructor to teach exactly "when" to flare and "how much" to flare, other than by letting the student work it out for themselves after a succession of thumps and balloons... "Ok, so that one was too late, do it a bit earlier next time..." Every bad landing reduces the student's confidence, so a few early acceptable landings help enormously.
Once the student has got the feel for it, they are free to use other triggers and perceptions to land the aircraft - such as may be required for your low vis example. Once your confidence builds, your field of vision expands from beginner's tunnel vision, so it doesn't matter so much where you focus your eyes.
At least, that's how the author described it to me a long time ago over a beer.
I think he found that there was a lot of opposition to the technique over the decades and that is why he has gone to so much effort with mathematics and trigonometry to "prove" that, at least in theory, it works.
I think there are still some theoretical holes in the mathematics, which explains why it doesn't always work as well as it should, but the idea still should hold well enough for acceptable landings. Holes that I have identified include no accountability for ground effect, prop wash over wings, thermalling in hot weather, and wind gusts causing increase or decrease in IAS during the flare. These holes can be corrected by the
experienced pilot during the flare through perception of the sink rate from peripheral vision and the G-forces through the seat of pants, for example. Hard to teach, but...