hummm?
i have always thought that i have fairly wide feet and asolos are my favorite when i need a big, good boot. i certainly could never fit into la sportivas, for example. those italians seem to have the most narrow feet. but my asolos are great. i normally wear a 9 (42) but i buy asolos in 9.5 (42.5) so that big wool socks fit for winter. i have had a pair of 520 gtx (old style) for 6 years now with over a thousand miles in them and they are still great. i play on ice and snow in a pair of annapurnas. they're like humvees for your feet. a little heavy but super stiff (great for crampons) and fairly warm for unlined.
on the other side, i bought a pair of some low top style second hand in my size but they never fit right. toe box too narrow with weird arch.
so, i guess it could be the style where they differ, but i can say for sure that my 520s run true to size and are definitely on the wide end of the scale.
hope this helps.