After reading elqasar2's post, I installed last 7-zip 18.05 on my computer, created a 7-zip file with password & encrypted file names, now results changed :
1) With last 7-zip version 18.05 (2018) :
2) With version 7-zip 9.20 (2011) I had on my computer during 2011-2018 :
But truly, my thought is you shouldn't work on that issue because it's not an issue : "unknown error" means the file (7zip, rar etc...) is passworded AND contains encrypted file names. Please dont spend your precious time on trying to get the correct message "cannot view encrypted archive" on so many archive extensions, depending on old or new version of each archiver etc...
If the file names show in Hover Box, that's great : it will mean the archive is not protected, or protected with a password only : that should be enough for all of us.