When I updated the CLD to Calculate Linux 18.12 update, I created the zz-autounmask files on the portage directory. These files only create problems. For example, I uninstall Chromium, reinstall with emerge -G chromium, the system says that the file does not exist. When I start the GUI Porthole portage system instantly installs a Chromium binary pack. Can I delete zz-autounmask files because they only create problems? When I look at the Porthole system, it shows that two versions of the same program are installed and they are not.
I do not think that these files are somehow affected, but of course you can delete them.
From my experience, this file has an impact because Porthole offers writing in zz-files, plus there are written versions of programs that are old, parameters that are no longer visible, programs that do not already have.
You are right, it is better to keep zz-files under control in order not to catch the lock in the future when updating.