Remove 8 character 'uniqness' requirement for usernames with MySQL 5.7+
As stated here:
If you plan to use MySQL® [...], the first eight characters [of a username] must be unique on the system.Indeed, this was an issue in MySQL 5.6 and older due to its username limit of 16 characters. However, since MySQL 5.7 that limit has been increased to 32 characters and thus the restriction in cPanel should no longer be necessary when using that database (or later ie 8.0).
For reference, this restriction was removed for MariaDB users years ago in 11.56