The pad wear sensor resides on one side of the pad. Going in reverse probably orients the portion of the pad with the sensor a bit closer to the disc...this is a miniscule dimension, but regardless, you are due for replacement.
MB does not recommend "turning" for any reson other than slight abberations on fairly-new ones.
Most of us have a different "3-coin" rule...replace the rotors on the "third" brake pad replacement interval.
Relative to the cost of pads, the rotors are inexpensive.
Rotor replacement is a DIY...just make sure you use Loctite on the bolts when you reinstall...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car