That was a good read. But, I can't say that I completely agree with your initial premise - that every instructor takes their students on Trust Me dives.
I feel like any truly good instructor, whether they are teaching the initial OW class or Adv Trimix, will adequately prepare the student so that every single thing the student does is something that are fully prepared for and comfortable with and it's a situation of the person taking a step to expand their own horizons - a step they are prepared for. Like a diver who who has never been deeper than 70 feet, but, on their own, when they are ready, they go to 80'. They are expanding their horizons - their limits, if you will - but not via a means that requires trusting anyone but themselves.
A new OW student should be ready, prepared and confident of their own ability to try sticking their face underwater and inhaling through a reg. Every step after that should be a case of doing what they know how to do and are prepared to do. They're just doing it for the first time. But, like going to 80' for the first time, they aren't trusting anyone else.
I'm not sure I made very clear what I'm trying to say.
We all get training and then we go on to learn and expand the boundaries of our experience on our own. That is not Trust Me diving. It seems to me that a good instructor would bring their students along in exactly the same way. Where every skill they have to perform and every action they take, even though it's the first time they might be doing it, it's a case of the student being ready and they are proceeding to expand the boundaries of their experience by trusting only themselves. The instructor is just there to observe - not for the student to put their trust in.
Back to your initial premise - I think a LOT of instructors do work the way you described. It's certainly faster. I.e. it takes less time to get someone to the bottom of a pool and breathing off a reg if you just say "here, stick this in your mouth and press this button and you'll go to the bottom. Trust me, you'll be fine." Working them up to that slowly, so that when it's time to go to the bottom of the deep end, they know what to do and are confident and going to the bottom of the deep end is nothing new or anxiety-filled - it's just a little deeper than what they did before. That would take a lot longer, for most students, I suspect. But, I believe (hope? have faith?) that there are instructors who do train that way. Though they may be few and far between.