As a freelancer, you always has to consider that other developers may work on a project after you do. Obscuring code or other items may make it difficult for someone not familiar with the code or website to make updates and changes.
I recently encountered just such a situation where the previous developer hid the Advanced Custom Fields (ACF) settings in the dashboard. At first, I was wondering how this was set up but then discovered a custom plugin which only allowed that developer to have access. Otherwise, ACF was hidden. While I was able to figure this out and add my credentials in the PHP code, it was not obvious at first and took extra time, delaying the project. In addition, if you are not set up as a developer, the ACF pro database update fails. This is quite problematic as you can still update the plugin – just not the database!
While there is nothing wrong with trying to protect ACF settings from inadvertent changes, restricting access via a plugin to one developer seems too restrictive.