Yes, but that doesn't explain why Simon should give Federer trouble when another 'grinder' - Ferrer - who also doesn't give away free points, also is rock solid from the baseline, and also feeds off pace is absolutely owned by Federer...?
I think Gilles manages to surprise Federer with his random injections of pace during the rally. Simon can flatten out his shots more than Ferrer and when he was at his best was able to hit some pretty impressive winners against the top guys especially on the run. Ferrer plays a more grinding style with much more topspin than Gilles, they're not really that similar. That's my guess but I don't really know.