All orgs should consider locking out all employees for at least one uninterrupted week a year. Very easy way to shake out all sorts of problems.
Could you give some examples?
As a simple example, it's very easy, when starting a company, to issue personalized email addresses to early employees and then people communicate using those email addresses. It's perfectly fine to email the CTO at first-name@example.com, because everyone knows everyone else and it works.
As you grow large, it becomes important for people to address roles rather than individuals. This way, if people leave their role, they can (semi-transparently) be replaced by someone else taking that role who will then continue to receive all of the same emails, be able to respond to them, etc. So then it becomes important to have e.g. a cto@example.com address. When the CTO takes a vacation, their email gets routed to someone taking over their duties, you don't need to communicate to everyone to start emailing somebody-else@example.com instead.
But sometimes it's not just about cooking the books: the last "SSL cert expiration" fire I lived through happened because the person who had credentials to Digicert had to take sick leave. It was never a documented/defined process because "just flip Tim an email" was always sufficient, Tim didn't mind doing the work, and Tim didn't like going on vacation.
Two week lockouts mean there's no chance of shadow IT/back channel work happening, and forces you to document your processes.
[1]: https://www.fdic.gov/news/financial-institution-letters/1995...
It certainly did shake out lots of problems...
(My point is that after having had that happen to me, if it EVER happens again and isn't cleared up within minutes, the sonic boom you hear will be my tactical resume deployment. I dismissed the warning signs as "minor glitches". Never again. However, if it is something planned and I agreed to it beforehand, I guess that's OK. On second reading, you might have been describing something like that.)