They talk a little bit about why they do it here:
3D models are mostly expressed as triangular mesh, which means that the final slicing and printing path are dense line segments. When the printer is slow, these dense paths have no obvious bad influence on print quality. But when printing speed is high, A lot of transient impulse signals will be produced at the turning point of the segment, which brings about noise and vibration.
In order to alleviate this problem, Bambu Slicer generates arc path by fitting within a certain acceptable tolerance.