I also have direct knowledge of a couple of other startups, similar size of 20-30 people in engineering, and they are about the same, no more than ~6 people.
In most cases, people really shouldn't be accessing production, it should mainly be deployment tasks that do. But you need a certain number of people to have access to cover failures etc. For example, having at least 4 people provides coverage if one person is on vacation, and then another gets sick etc.
I've read other companies basically have every engineer has production access to what they deploy, not sure I agree with that approach but I can see the argument.
I don't have access to approving the pipeline to release to Production, but that's just a permissions thing that we only realized last week I didn't have when I was to manage the release while my boss was on vacation. I'm the tech lead of the project with four other developers on the team.