Provide information in between exercises being added to Exercism, and them being unlocked for a user.

I just came to a problem similar to #3867, #4769 and a few similar ones.

I can see a new exercise in Racket track, unlocked by a completed exercise (in my case it is "Affine cipher" and "Bob").
It took me several minutes to dig through closed issues to find the information about a script that takes hours to complete and needs to be run manually.
When I enter any core exercise of the track, it displays: `Carry on coding. You have 1 unlocked side exercise that you have not yet completed on this track. Why not try a new challenge?`

I know now I need to wait until the new problem is unlocked, but maybe there is a way to improve user experience? Maybe new exercises should not be displayed to users until the database is updated? Or should be available to everyone for a few first days? Or explicit message could be displayed "this is a new exercise, wait until it is added to your track"?