I thought you might be telling us the Left Rear had Left Hand threads! I was having tires installed on our old Class C (1983 E350) and fortunately was at the coach as a "tech" was struggling. Used to be common to use Left on the Left, but ours had Left only on the Rear. Left Front was Right Hand.
I follow "trust bur verify" when it comes to this stuff. Send On our cars, I'd find a couple nuts loose, couple nuts over tight... It was a Ford-something (we had a TBird and an Aeroster) and I found the left front so tight I went to a 3/4" breaker bar to loosen them. Re-torqued and never had a problem. I've heard of over tightening warping the rotors/drums, but that didn't happen either.
You're probably OK. That's from my "domestic" vehicle experience, and I doubt MB uses sub standard hardware.
Torque Stick is only good when you tighten up to the torque spec "from below." If a shop guns it down to more than the spec, then switches to the stick... Well, it won't tighten any more, but it sure won't back it down to the right spec.