Yes, it is based on Android. My only hope is that such a pared-down phone might remove a lot of cruft. But who knows 
? Abundant marketing + fact scarcity.
There is also the Librem 5 from Purism. Mobile Linux/Gnome/phosh is nowhere near as polished as Sailfish OS but has evolved quite nicely from its first inception. Still a way to go, though, especially when it comes to battery drain.