Yea, I found that too, but come to the same conclusion like you.
I didn't recognized any differences.
I'm thinking about the reason why people just change from D version to M version and I can't figure out any reasons...
From my side, that letter D or M has nothing to do with the repairing.
That peoples are just put new parts on the pcb and if one of them failed before with the old parts which was the D version,
now is working. Not because of the D or M version but cos the new parts.
Conclusion, changing all four parts with new D or M parts can maybe repair the unit.
But strictly searching for the M version of the IC has nothing to do with the repairing.
Maybe I'm wrong, but this is how I see this stuff.