"Easily"? I thought it was a system level thing? I don't have to sign in to Windows with my developer account(I only use a local account) to use Visual Studio or access the account MSDN/community stuff.
Plus, it'd be very hard to accurately determine "correct" usage. You don't have to have a dev center account to develop for Windows. You just need it to distribute your apps. I've made plenty of apps without distributing them and haven't needed to touch dev center. I do believe you need VS to create the apps, but only because the tooling is only available there. There's nothing technically limiting that, though, and simply having VS installed does not indicate you are developing Windows apps. You could be writing Python, for example, or even writing stuff for Arduino using 3rd party extensions.