Based on a report of a player,
It appears when a player gets their alt banned, these new entries are not visible in the ban list unless you’re searching for them.
As far as I’m aware, this is not documented anywhere.
Searching their userid in the ban system yields this result:
Looking through the bans normally looks like this:
Checking the more column yields nothing:
I also tried doing a test by adding my own ban on top of this, and it simply erases the Roblox auto alt-ban instead of adding to it.