Schematic Editor | 7.0 | English | Documentation | KiCad states (in section Net name assignment rules) that global labels have precedence over power symbols, which makes sense. Why go though the trouble of adding labels if you don’t want to use their name?
Local labels do have a lower precedence though, so that can work.
One solution is to work with net ties. A net tie is a (small) footprint that connects two different nets together. You can also use the Solder Jumper footprints (Either NO or NC) to make it easily changeable on the PCB afterwards if you like.
Another option is to just connect them all to GND, and optionally add a text box with some comment on which pin relates to which hardware version.