Well to make this one clear: there is nothing weird in not having the latest Plasma in testing branch. Testing is used to get packages into the branch which will land in stable at some point. Latest packages you will always find in Unstable with the caveats when libraries or other things force us to do rebuilds of our own overlay packages.
Also within the release team and KDE ISO maintainers we discussed this when 5.25 is ready for us. It will be part of 22.0 release of Manjaro,which may come out in several months. Till then we keep 5.24 as given, since we shipped that with Ruah release. Those who really want the latest and greatest can always switch to Unstable or even get involved into the Manjaro development.