Guard isn't easier. Guards are usually lead interior rush blockers, pull leads, identify delayed/ gap blitz, and they usually match up with pass rushing interiors. There is nothing easier about playing Guard.
Other than pulling (which they do just not as much), Centers do all of those same things.
I think what he meant was Centers are typically the ones who make the blocking adjustment calls. With the shortened off-season and pre-season to learn from, it would be better to leave McCoy there since he already has experience and the knowledge of the offense. Not to mention chemistry with Drew on snaps.