I did read that article when it was first posted. It has some good info in there.
I have been getting paid to coach mtb for quite a few years now and am aware (and use) the dropping of the heels. I use it on the regular even while clipped in on my HT. Maybe it's just years if riding clipped in and not having any desire to change that on my HT? I have tried flats a few times and really gave it a chance but could never get rid of the bouncy feet.
As an aside it's interesting to see changes in what/how technique is being taught over the years. For a long time the mantra was 'stay low and aggressive'. In the last few years the 'stand taller on the bike' is the new mantra. Neither is bad I just find it interesting that the focus changes for coaching/instructing as things progress. Maybe it's the equipment that plays into that? Because bikes are longer and more stable now it's easier to stand taller more often?
One technique that I feel transfers very well from the HT riding is braking less because that makes the ride smoother on an HT. However, that does lead to some exciting moments at times! As you stated the margin for error is much smaller on an HT which makes the commitment to lines full on!
I really want to get a hold of an ESD frame and build it up so I can find out if I got anywhere close to the same ride feel with my current HonzoST build.
I do think that I will always have a hardtail in the stable. Specifically a steel hardtail. It's fun to ride the same lines as I do on an FS bike but you need to change how you do it on an HT.