Just like everyone else here, I've been frustrated with the file name reselection issue. By fluke and trying different things, I have managed to stop the issue in my Windows 11 system by going into the File Explorer, View menu selection, Show - File name extensions "Unchecked".
You will notice the "I" bar will still flash for a couple of seconds, but it doesn't reselect the file name and you can make your changes without overwriting the entire name.
Seeing how this has been an issue going back to Windows 7, I can't believe Microsoft hasn't fixed this. I guess most people don't have extensions shown.
Lastly, if anyone else has figured this out and I missed their post, it wasn't intentional.