> Is there a reason it should be done, as you say later it's purely about version numbers?
The reason is that KDE makes a versioned release as a consistent whole. They never
guaranteed mixed versions of Plasma related package to be compatible (either backwards
or forwards). So having such mix is always a potential for any kind of problems.
See how KDE Neon releases are done for instance to compare.
Regards,
Shmerl.