The protocol says that a client can return 'notStopped' as the response when processing a message that would require the process to be stopped. In all-stop mode (what we have now, see bug #30470), I think this should affect essentially all commands except 'pause'.
I have a patch.
https://sourceware.org/pipermail/gdb-patches/2023-November/203868.html
I forgot to stick the "Bug" keyword in the commit message, so it wasn't logged here...