I think its a bit of both. Mostly cosmetic as a lot of "stuff" will fall out of suspension giving a clearer appearance, but from what I've learned here is that some of the "stuff" might not allow the beer to be all it can be, thus a bit substantive.
I don't think it'll clean it up like say triple distilled vodka and be utter hangover free. Interesting theory though. I,d brew up a session if you want something you can knock back a few not feel like crap in the AM. I love British style session beer for this reason, so far all the brews I've done are under 5%. I have a Scottish 70 in the primary now
Good luck and keep me posted.