On my another Nvidia laptop we get some weird refresh rates from xrandr 1.0 (there is fallback to xrandr 1.0 with Nvidia proprietary driver). XRRRates returns those strange values (51 max for max resolution mode here, while in reality that is 120Hz or 60Hz). I didn't dig much into that why is it so
That's from NVIDIA DynamicTwinView. See WineHQ bug 34348 for example.
As a bottom line, I see p. 1. as more of an issue here, do you still think we should pursue timing data from EDID and use Display Range Limits Descriptor if present, or rather leave it as it is now?
It seems better to leave it as it is. Thanks for the clarification.