Not sure if it’s still the same as it was back in my day, but KDE’s “release candidate” nomenclature was always a bit of a misnomer. You’d never see RC1 actually released as final. What it really means is that the alpha “feature refinement” beta “bug fixing” phase is over, and it’s the final testing phase for showstoppers. However, the definition of showstopper seemed always to be very wide. Thus, a lot of bugs still get reported and fixed during this phase, and RC really means “beta, but towards the end of the pipeline”.
Which is in contrast to the Linux kernel where a RC can be declared ship-ready and simply get renamed.
Admittedly there’s a fairly large impact difference between kernel level bugs, and say a bug in Okular…