I found an issue regarding zone filling in version 7:
By adding ground plane on a layer in KiCAD 7, we can see sharp corners around pads which have thermal relief.
However, there were smoother corners in KiCAD 6:
Are you sure this is really an issue? The usual manufacturing tolerances are way larger than these tiny corner radii and the way PCBs are etched/manufactured will smooth corners out a little bit anyway.
I think in the settings there is an option to enable the old zone filling algorithm, but I wouldn’t deem it necessary here.