i would think only the poll would be affected and its only realy mauls that have been treated. And i think most people tend to drill them out now rather than burn unless you get caught out on a trip, good point thoughI gotta admit I get a brand preference sometimes too. With axes my softspot is for Plumb but they're no longer being made.
I've sharpened my axes to shaving sharp before just because I could, but I gave that up years ago and just went back to my old farmer/logger roots. All an axe needs is a quick sharpen with a file and go to work. As you say, duller is better for splitting (3 generations taught me that) As for the heat treatment, don't you reckon that goes out the window the first time you burn out a broken handle to replace it?