Error when trying to do $out in admin schema

Hi Folks,
We have Single node Mongo 4.4
We spotted an issue where we have deployed to wrong schema and this has resulted in us trying to do a $out into admin schema and it is failing. We are in the process of redeploying to correct schema.
I understand this issues is not permissions based but a default setting that doesn’t allow you to $out into admin schema.
In order to document the problem I just wanted to find something / document online explaining why this doesn’t work and I have come up with nothing. If anyone has a link / doc that specifics why this doesn’t work or states that this is a default in admin schema.