I checked the documentation but I couldn't find anything to show this to be a problem other than that the practice is discouraged.
It's really nice when you have to hire someone new for the position. You add them to the DL and they're automatically in control of all those accounts.
I have no idea why more companies don't do this.
Still on Amazon to clearly tell people it is this way so they can properly plan for it, but employee's email addresses really shouldn't be used for the root account.