I admit it adds some intrigue to see the Rams make this switch. But that doesn't mean they're not satisfied so far. The goal is to be at the optimum.
I've heard no reports, including after the scrimmage (which media did attend) that the right side of the Oline didn't perform well. Further, as one article pointed out, Ingram spent much of his time causing trouble against the LEFT side of the Rams oline, not the right side.
McVay says they are experimenting. And the reason is to always be certain you have the best possible combo and to gain flexibility in case of injury. No reason at this point to doubt that (he's not Fisher who sand bagged on everything). We really don't know yet what McVay means by what he says about certain situations.