I find it odd that Microsoft limits their Office Mobile apps to Office 365 subscribers. To me, it makes sense that if a machine is running Office 2016 (or whatever the most recent release is at the time) should have full access to the Office Mobile app suite as well. I say this because it's useful for 2-in-1's (SP4 in my case). Even though the apps are pretty limited, they're way easier to work in when doing a quick edit in tablet mode versus using the full desktop suite. I'm pretty sure Microsoft can find an easy way to check a machine for a valid Microsoft Office 2016 license to enable such a feature.