The template is immediately contradicted by a Real-Life example that actually shows it can be made possible (though whether it'd be worth it is a whole other discussion). Would a removal be in order?
Topic on Talk:Impossible Hourglass Figure
Since the example given is conjecture and does not refer to a specific person or style, it might be feasible to move it to the article, with the "No Real Life Examples" tab being put immediately afterward.
That seems reasonable, possibly with a comment to the effect that the "impossible" in the trope name means "Impossible in nature" rather than "simply can't exist".
Yeah, that's a viable compromise.