I guess I'm misunderstanding the way the rule is written then.
7-1-7a. It is a false start if: A shift or feigned charge simulates action at the snap.
It's the "at the snap" portion, shouldn't this be "before the snap" if the play I described is a false start?
The "at the snap" phrase is describing what the false start looks like. A false start looks like the action a player would normally exhibit at the snap.
For example, a lineman either "fires off," or drops back in pass pro at the snap. If he does that before the snap, he has "simulated action [which normally occurs] at the snap."
Hope that's helpful.
In your case, If the RB has "simulated action [which normally occurs] at the snap," then the lean and step is a false start. I agree with Bama and Ralph - I'm throwing a flag for a false start.