Production mode and the develop you see in the About are two very different things.
You can run your app in two modes - Developer and Production. You use developer mode on your development or testing machines/servers. Whereas you can setup your servers which will be accessed by the end users in Production mode.
The develop you see in the About menu - is the name of the branch that your app is currently on. Branch is the git way of stating what version of the app you are on. As far as erpnext is concerned, develop contains changes that may come in the upcoming versions and is not considered stable for Production servers as it is Work in Progress. Meanwhile, master branch is the stable version of the app which can be used for both development and production machines.