That's what I had thought, however the one part number / calibration across the cars I mentioned clouds the issue. I will be swapping modules around this summer

And, a 97 C class could have come with 3 channel ABS or 4 channel ABS / ASR. The 3 channel car has a speed sensor on the diff pinion and the 4 channel at each rear wheel. Somehow a control unit needs to account for the differences. I'd think the 3 channel car would be immune to a rear ratio change unless a module somewhere is comparing front wheel speed to pinion speed.

There is absolutely no way the trans computer is looking at front wheel speed to determine shift timing as there will be too much room for error due to tire size / road slippage