That would be a giant PIA if I had to do that as a shop mechanic for every bike with a dropper and is unnecessary overkill.
I don't even have a dropper yet but I've ordered one and I've specifically chosen an external-routed one. It literally takes seconds to unclip the cable and pull the post out. Another few seconds to drop in an old seat-post. Many internal-routing posts also have quick-release cable fasteners at the base of the post. $25?
It seems to me that the desire to clamp on the dropper is not driven by a strive for best practice. I think you just want to justify doing it because it's the quickest and easiest thing to do. It's about saving time and money, not saving the dropper post. But what do the people who make the posts say?
Specialised Command Post:
"CAUTION: When placing the bicycle in a workstand, do not clamp the bicycle by the seal head or upper tube section as they are both part of the air seal system inside the seatpost"
RockShox Reverb:
"To clamp a Reverb equipped bicycle into a bike stand, loosen the seatpost binder bolt/quick release at the frame. Raise the seatpost to the Minimum Insertion line then tighten the seatpost binder bolt/quick release to the frame manufacturer's recommendation. You may need to detach the hose from some of the cable guides in order to raise your seatpost to the Minimum Insertion line. Do not exceed 6.7 N∙m (60in-lb). IMPORTANT:clamp the seatpost into the bike stand just below the top cap. do not clamp the seatpost by the top cap or allow the hose to be clamped as this may damage the seatpost"
Thomson Elite:
"It is not a good idea to use the seatpost to hang the bike in any way. In a work stand, it is possible to crush the outer tube when clamping pressure is applied. If you are supporting the bike by the gold stanchion, you can damage the internal components."
Fox Transfer:
"The anodized surface of the upper seatpost, like a rear shock body, serves as a sealing surface. Always take every precaution to avoid causing abrasion damage to the anodized surface of the upper seatpost. The upper portion of the Transfer seatpost may be carefully clamped in a workstand. Do not clamp the cable pulley mechanism of collar cable routed Transfer seatposts."
So the manufacturers say that either you must not clamp on the upper tube at all, it's not a good idea or you can do it but you need to be careful not to scratch the coating. Would you clamp on the stanchions of your suspension fork? No? Well it looks like your bike mechanic would.