It does to new users migrating from mzscheme. Not everyone is going to downgrade mzscheme to 20 revisions old package just to try out new lisp dialect.
Bringing it up to date would probably increase its adoption.
I think he meant that updating Arc didn't make any difference to the requirements, not that using an old mzscheme doesn't make any difference, which it certainly does. I wouldn't be using Arc if there hadn't been a patch to get it working on newer mzschemes; the git "wiki" (http://git.nex-3.com/arc-wiki.git) works on said mzschemes right now. It may not be official, but it might help scratch your itch.
