Modernize your SharePoint team sites by connecting them to new Office 365 groups

IMHO, documentation is important but not enough. You may not read documentation, you may not read it carefully, you may understand it. Software itself shall alert somehow if you use wrong function. If 'everyone' shall not work it shall not work from the moment when you try to add it.

What is the current scenario - you add 'everyone'. Test behaviour with few users, it could take couple of days, everything works fine. On third day you deploy the change and announce to the company.  On next day after that someone requests access, you check - 'everyone' disappeared. Add it again since you know it worked and you know 'everyone' works for a long while on other sites (yes, on couple of our sites it works probably for months). After that you are asking other admins and owners who the hell removed 'everyone'. Nobody. In a while cycle repeats. Finally you check the log and see what the system removed 'everyone'. Start checking all your settings, nothing. Open the ticket? - but if they don't know the answer they ask to do all the tests they know and reinstall everything from scratch, plus it takes a lot of time. Let check on TechComm. Uh, I'm not alone and that is by design...