I disagree on that. I think the ski should come off of the snow because of the transition. It should feel and look more spontaneous. The bottom line with any of these drills though is that you can/should tweak them to highlight the skill you want to highlight.
I've been told from multiple sources that the initiation for the WP drill should occur with 100% weighting on the new inside ski. Some would consider the transition movements to start in the fall line (i.e. the edge change is just a continuation of edging movement started in the fall line when the skis started reducing edge angle). In this case I can see where your viewpoint is coming from. But if the new outside ski comes off the snow because of the transition, what is the transition mechanism that causes this? I'm having a hard time visualizing anything but an up move doing this before the new edge is engaged. This clip demonstrates that technique. But I'll bite. What feedback would you give this skier?
I agree that WP turns can feel and look more spontaneous. I've seen short radius WP turns that would be seen by a non-instructor as "just skiing" (i.e. they cold not tell you what was "wrong"/different). I've felt it briefly but I don't own it yet. Your skiing is ahead of mine and you have more access to stronger coaching. One breakthrough for me was continuing the extend/flex movements of the lifted leg when there is no snow contact.
I'm all for varying the part of the turn where the ski gets lifted off the snow in a WP turn. My bottom line is that if the ski comes off the snow after the skis have gone flat, then this is not a WP drill. Does coming off the snow because of the transition mean before or after the skis go flat?