Ok....I'm going to be cast out for this one...
I MUST say that guy doing Pivot Slips or what I would refer to as drifting is doing it perfectly and is a fantastic expert tool to use between monster bumps, droping into steeps that are grassed up, rocked up, narrow enter. I have spent hours at all mountain clinic perfecting this tool!
I will guarantee you if you can do that as well as the video demonstrater does, it means you have full control of your edged to edge transition knowing how to fully utilize the flat portion of your ski during transitions.
It's all in the feet my fellow skiers....it all happens there and if you can do it slow and in contoled, you will open up loads more all mountain terrain! 
Ok...cast me out .....I can take it! 
agreed
the thing is pivot slips are not a dead movement pattern. Like(only) tipping to turn is. They also dont require muscling anything, and there is a fine tipping movement involved as any turn or pivot starts with a edge change also know as tipping. Active rotary although not used much on a short wimpy SL skis on groomers or off trail is a necessary evil in skiing real terrain on real skis.
I can tip to turn and bend a ski better than most, retraction extension whatever. Tipping to turn is easy and doesnt show a mastery of anything and is dead end limiting technique. It limits you to terrain where only that technique on those skis will work. Since this crowd is pretty much into groomer skiing by default of their dogmatic skis and technique choice I guess thats fine. The thing for people to sit here and say they use a ski technique where any active rotary is non existent WILL limit where and what they can ski, it will also limit what kind of ski they can ski on. Suddenly a 30 meter big mountain board that would be great for alot people cant be skied because you have forgetten one component of any turn.
so cliff notes
A. show me someone who can Pivot Slip well, and has skill blending so that every turn isnt pivoted you have shown me a true all mountain skier
B. Tipping to turn works on hyper sidecut skis, in more open places but DOES NOT work in real terrain, in real conditions, on real skis
C. short carvers are NOT all mountain skis, heck all mountain skis arent even all mountain ski.