Yep, you got an unrelated error from a CentOS repo: [Errno 256] No more mirrors to try
In the past there was a bug but in your case the lock was working, but some of the locked repos could be unavailable or an extra upgrade step required. Nonetheless, leading to problems surely isn’t the intended behavior.
From command line most repos pointed to the locked version release but the ones that don’t support minor versions (epel, scl…), IIRC.
Release lock has been modified to always locked and manual upgrade to new release, IIRC: Ultimate ns7 software updates origin policy