Mapping spurs with same number as parent motorway, A road, etc

As I was just thinking, it crossed my mind on how road spurs which share the same number as their parent road should be mapped. Should they be mapped as links or as roads in their own right? I’ve noticed there’s been quite a bit of division across the UK as to what spurs should be mapped as!

In one case, the M6 Bryn Spur was previously mapped as a motorway link, whilst the M25 Sevenoaks Spur (for the lack of a better name?) has been mapped as a motorway in it’s own right essentially since it was brought into being on OpenStreetMap.

If any light could be shed onto this topic it’d be greatly appreciated!

Kind regards,