If the number of people who are on the team can fit in a single room, then the release process can easily be run on the laptop of one of the team developers. I don't see how any team of five people consistently releases quickly enough that you would have multiple people trying to release at the same time. A small team should not require tooling to enforce that tests are run before production deploys, that should be either cultural, or part of the script that is easy enough to run on anybody's machine.

Most people do not need CI until you have a separation of concerns (i.e. code from credential management) that are managed by different people/teams, and therefore all of the decisions cannot be made in a single room.

I do see being able to run test matrices across multiple OS or device options as a reason for smaller teams to adopt CI early.