When we create a 'prime' kit, the idea is that it is snapshotted so we can stabilize it for users. The name is supposed to reflect the version of the main thing in the kit. It looks like we chose a bad time to create 5.10-prime but the general idea would be to just do bug fixes on it until it is very high 'prime' quality.
It may have been better to create a 5-prime kde-kit and that is something we could look into doing instead. I don't use KDE so I need input from others about what is likely to be stable over the long haul.
The goal of a prime kde kit is to just get everything working consistently for users. It may not be bleeding edge but it will be a good starting point. And then we would roll out newer prime kits that are also stable, etc. so the changes would come in controlled and tested groups rather than dribble in as they do now.