The problem with this is that it doesn't account for min versus max endstops. The "home position" for a max endstop might be something like 300. Simply setting the home offset based on the current position assumes that the home position set in the configuration is always going to be zero. The logic needs to account for the difference between the current position and the endstop — so the current implementation simply works from the distance between the current position and the nearest end of the axis.

Recent issues with M428 are probably primarily related to the broken report_current_position function, but might also be related to the fact that we changed soft endstops to use the borders of the printable (bed) region and no longer the hard endstops (MIN|MAX)_[XYZ]_POS. To revert to the previous (non-broken) behavior, the base_min_pos() and base_max_pos() might be better than soft_endstop_(min|max) here.

The website describes M428 this way:

The current position is set to the native home position.

It doesn't describe the case where "home position" is something like X200 Y0 Z0 so that needs to be added. But the idea is, shortly after you home, you would move the axes a little until you have your preferred position within the bed, but relatively close to the endstop. The M428 command makes the current point correspond to the configured endstop position by setting home_offset appropriately.