Re: Is this a bug? GPU scaling option results in a different refresh
I know it's confusing, but that's what the GPU scaling option does: it drives the panel at its native mode (including its native refresh rate) and scales the requested mode to that. In particular, that means that the requested mode's refresh rate is ignored and only its dimensions are used.
We've considered adding code to do like you suggest: try to find an EDID supported mode with a matching refresh rate and switch to that, but it hasn't been implemented yet. For now I would suggest just disabling the scaling option.