Except in this case the alias does not call itself directly but through /scid, so the restriction mentioned in the help file doesn't apply.
The problem is indeed caused by recursion but it has nothing to do with Windows. The "error allocating stack memory" is just mirc's way of saying "you reached a recursion depth that exceeds the limit I have set" (which varies among versions and is currently 85 for /scid-mediated recursion - the most you can get is 255 by mutually recursive aliases called as commands, not as identifiers).
