The dealer had a cone on hand to demonstrate how he can stand on an 8 grams 6 cone and not break or bent it. Very impressive.
That is amazing!
Light weight rigid cones are very attractive for rigid "piston' behaviour. The ability to control them with a small motor makes them very efficient, however, the issue then becomes one of managing the bell-like ringing rather than break-up. Soft viscous dense damped woven materials whilst less "pistonic" dampen this ringing at the expense of higher cone weights and more massive motor structures and a more limited frequency range before they "break-up"....a trade off if you like that results in inefficient drivers with narrower frequency ranges. Some materials/geometries provide a good balance for damping with both light weight and low cost - such as polypropylene woofers.
Another issue is beaming - this causes a reduction in the power response in the upper mids (even if on axis is ok) and will make a speaker sound less harsh at elevated levels. 6 or 7 inch cones are less well suited to upper mid range frequencies but 3 inch drivers, which are better for upper mids, suffer in generating the necessary SPL's at lower mids due to the large amounts of travel required and the difficulty in maintaining alignment on a small structure. Some speakers use two mid range drivers to help overcome this issue in a Dappolito arrangement. Some will simply accept to take a dip in the mids at elevated levels. Some will crossover the tweeter lower to limit the beaming but then run into tweeter compression issues at elevated levels (again a dip in the upper mids).
It is all a balance of compromises at the end of the day. So while I agree that pistonic is ideal in some ways it is another design factor in the grand scheme of things.
The MAGICO constrained layer damped cone is what impresses me most as it apppears to use a sandwich of rigid pistonic material constraining a viscous layer in the middle which acts to dampen the ringing (it shears when bell-like behaviour occurs in the outside rigid materials). Finally, an extremly rigid pistonic cone that may not suffer from too much audible out of band ringing. It may not address beaming from cones but it will likely be extremely linear and low distortion (accurate) particularly on axis.