Using 5.23 (the latest version from CKAN), I find that there's a delay before the available experiments are evaluated. For example, I did a lot of Mun, Minmus, and Duna exploration in Career mode, but [x] Science! acts like I haven't even done the space-situation crew reports yet.
Screenshot 1
If I go into the R&D archives, it's clear that many of those experiments have already been fully run.
Then, only after visiting R&D, [x] Science finally updates to show what I've done.