It is obvious what exceptional tech means. It means Nathan Chen doing 6 quads.
A happy new year to everybody!
Well, this is not at all how I see tech in figure skating, so it mustn't be that obvious.
I follow on men's, as you started, though this is not the subject, because differences are more extreme.
Of course doing 6 quads
is exceptional tech because only him can do it (Yuzuru Hanyu seeming to have decided to skip 4F to focus on 4A, and having less-than-ideal training conditions at the moment, preventing him from being "top").
But his competitive programs are so much lacking tech on all aspects but jumps, tough exceptional, it can also be called very unbalanced and partial.
Tech-wise, he would not be able to skate, not only Yuzuru Hanyu's programs, quads replaced by triples, these are really too "exceptional tech" — even his programs from when he was younger than Nathan Chen (because when comparing them, we tend to forget the latter is more than four years younger) and was still inferior to Patrick Chan in skating skills (he overcame it in 2016-2017, so, older than Nathan Chen's present age); or Jason Brown, who's Yuzuru Hanyu's age; but to Roman Sadovsky's or Jun Hwan Cha's, for instance, the latter being the same age as Nathan Chen, because he doesn't seem to be able to endanger his balance, either in step sequences or in spins for instance, as they do, and as in fact all other top Men skaters do. Also, his jumping with such long entries is a tech fault, his stiffness in jumps landings too (when I see what is written, and what Yuzuru Hanyu himself said, of his landings in Let Me Entertain You, still so much softer than Nathan Chen's!) He also tends to keep a medium speed, and indeed I don't see how one could land so many quads without, but tech-wise, he's lacking steep accelerations and decelerations. I don't think he would have the stamina either for a Yuzuru Hanyu program, even without quad, because they are so taxing. On the same ground, Nathan Chen doesn't manage to make his moves look effortless, which is a technical ability as well as an artistical one. (I know I'm missing some.)
He's obviously exceptional element base value-wise (and indeed real core of jumps-wise), but this is far from being all tech, and he's "exceptionally" (for a top skater!) deficient in all other tech matters.
I don't see such enormous differences among Ladies. If you take the "quad queen" for instance, Alexandra Trusova, she has not only quads, she has difficult entries and transitions, she shows very good skating skills, spins, flow... Of course all this lower the probability of landing her quads successfully, but she's 16 and I have great hopes that she gets technically close to Yuzuru Hanyu some day, or who knows, better? She's on the way. (We cannot compare with his level at her age because boys tend to grow later than girls.) and other Russian "quadsters" (or "nearly") are rather better than her on these tech aspects, though not dramatically.
So, for Ladies, we can say that Mariah Bell is not up to Russian Ladies tech-wise, but this is also a question of generations! And I would say, at last Nationals she was better than Alysa Liu tech-wise too, whose 4Lz should have been downgraded, I suppose you agree, and whose general tech level shows her age, which is quite normal of course.
Her precise arms and body movements are both of technical and artistic relevance.
And I will disagree further on The Guardian on the artistic side, because I think both are good, not exceptional, artistically, of course Mariah Bell being more "polished" but then, I love so much Alysa Liu's style (she should have been a Parisian) and am a bit indifferent to Mariah Bell's... which is quite subjective, I'll admit.

And I won't always agree with The Guardian about ballet either. After all we all all different in our eyes and ears, and in the way we process the information we get from them. But regarding tech, there are ISU manuals and things can (should) be measured, and there are multiple factors.