Absolutely agree, Seiler flip-flaps between what he means, much like Coggan, it's very hard to actual pin down what their current position is. I bring in Coggan, because despite the fact he has become almost a parody of himself and an internet troll on the time trialing forums at times, we can apply a lot of his metrics here.
But if you speak to Seiler, he will tell you it cannot be polarised this way, from a pure definition point, in the sense that the word itself means opposite ends of the spectrum, whereas a lot of this training sits more in the middle of a scale. I actually think you could just call this sweetspot training, as it's clear it's much like the cycling power zone that is specifically designed to create as much CTL, without crushing you. That's basically what is happening here, just without the use of a power meter - and obviously the impact of running means we can handle less (for instance I could easily rack up 100 CTL on the bike, but 65 now from running probably feels as hard, if not more than generating 100 cycling). I've spoken to Hard2find quite a bit about this and there is definitely an opportunity for someone, somewhere to make something better to apply to running. Using TSS I still think works for running, but probably only if you apply it to this model of training. It still totally underrepresents the really hard sessions. But then again, NP on the bike can be manipulated and broken, so maybe nothing is perfect, but I digress.
I wouldn't say it's fair to say I copied KI, I noticed he was doing something similar in terms of running that myself and others had been doing for over a decade in cycling. But he certainly inspired me to just go back to basics and have the confidence you can of course train like this, with relative success, not just on the bike but running. FWIW, I've not seen enough people doing this long term in running to comment, but absolutely nobody I encountered on the UK Time Trial scene didn't increase their FTP if they stuck to this as their training method for a decent period of time. The Strava group is interesting, which is why I haven't posted here much, as you can see who is training this way and their successes.
I also agree with you that 3 zones Seiler presented isn't enough, again they have changed over time. I think he's more in line with a 5 zone model now. Obviously as you say, saying anything below 2.0 mmol is ridiculous to say that's "easy" and zone 1. If I ran the top end of that , each day, I would be totally and absolutely crushed and there is no way I would be able to run the 2.5-3.5 mmol sessions 3x a week I target. In fact, I suspect I would get injured or something if I ran 4 days at the top end of Seilers zone 1 and then tried the 3x sub threshold days.