I wrote a ‘free-standing’ GCode optimiser / linter, which I’m still working on.
https://forums.maslowcnc.com/t/command-line-utility-to-clean-gcode/
I don’t have it doing arc to arc (G2, G3) deduplication yet, although I’ve had a go at it. It does do a lot of other path and general GCode optimisations though, so it still may be useful for you.
One of the big reasons for writing it is to try and reduce the number of commands generated by some overly finicky path fitting algorithms that different GCode generators use (Fusion 360, estlcam, etc.)
However, there is another bit of behaviour that could be happening here, although considering its MakerCam I’d say probably not. I’m pretty sure for Fusion 360 at least that there’s an option to get it to ‘slow down’ when going around corners, maybe MakerCam is doing that? (but again I don’t think so)