Liam,
I look at tips as visual or thinking cues to help me accomplish a movement, position or mental picture (I am probably leaving out aspects - no coffee yet this morning).
Example: JF's "elbows down" is a visual cue that helps the skier to counterbalance. I get this.
The "happy feet" bothers me. First thing in the morning, after a chairlift ride, I do tend to do some stretching - whether stationary or moving (minimal grade). My first run, I am concentrating on technique as it will tend set my muscle memory for the day. The feet shuffling of the "happy feet" video would tend to throw off my concentration on fore/aft balance that is critical, for myself, during my 1st run. I feel the reply coming," if you don't like the tip, ignore it". Don't worry, I will ignore it.
On the other foot (pun intended), the feet shuffling may be helpful for helping with ski boot bite.

"Mostly, I'm just using his (i.e. Foster's) free skiing segments as a demonstration of a skiing style...along with (now) 6 other CSIA notables." - I do not see Foster's skiing style the same as the other skiers that you have provided. To break it down further, I see Foster's skiing closer to PSIA with an extension release. Michel and Beaulieu ski with a flex release, closer to PMTS.