Even if the jack is a TRS, it doesn’t tell anything about the required wiring, internal resistance nor the best/expected taper type 
So it actually doesn’t tell anything at all, except that the jack is a TRS 
If MM would ignore the ring from the TRS jack then it would expect a TS plug. It would make sense if the functions of tip, ring and sleeve could be programmed in a firmware update to support all the possible exp options 
One question is that even though there is calibration, the range of supported internal resistance could still be limited
Edit: The TRS jack does imply that a TRS plug is required, but that’s all that it does 