A 220 grit will always be 220 and so on, the depth of the scratch wont change, the sander just helps removing scratches obvious to the eye while the surface its bare and dull, cover the scratches that cut across the grain that you notice when varnishing (thats why handsanding should always be with the grain) and the signs left by clogs on the paper, the fact that you dont feel it its just because it puts scratches over scratches in every direction, then it might feel smooth but the surface its inevitably scratched and if you wipe, not brush, or spray a thin coat on it just to get some shine you should be able to see them, the only example i could make its glass and suede, glass its smooth, suede feels smooth but its not in the condition you would want a surface to be prepped. Its obviouasly faster and feel smoother than when hand sanding, for the same time, how could you move at the speed and change of directions of a powertool by hand?
The auto body industry would have been on that like hawks if it actually worked that way, and if you try to do some paint jobs on body panels you will soon realize that what feels and looks perfectly smooth it not necessarily is once the topcoat goes on.
Trust me, the routine sand wipe spray sand wipe sand wipe and so on is there for a reason, no shortcuts unfortunately, try a test panel with the normal sandpapering routine and one coat of varnish and then put it beside a panel that had a 220 and a coat of varnish, then youll likely see the difference. And obviously, using thick coats of paint to fill scratches you would be able to see shining a light onto the paint job its not allowed.
It might be ok for under the glassing, but its quite aggressive for a thin piece of cedar, it creates holes and weaves too easily, better on hardwood if you want to skip a couple grits but not to avoid the final sandpapering and varnish right away.
For me getting handy with a plane and a fairing board, and practicing to reach the best glassing job possible its just easier and at the end faster or at least more pleasant.