The pin with 15 Bf4 is not forcing Black to defend. Black should try 15.... Nxc4 ie; 16 Bxd6, Nxd6 or 16 bxc, Bxf4 17 Nxf4, Bxe4 and Black has the better game.
20 Nxe8 is a matter of style to win. As you point out, 20 Rxe4 is solid way to win and what most people would chose.
Maybe, because you did not play your normal Ruy Lopez, that at the end, you also chose to be different in how you chose to win.
Just killing time and ran into this. Don't expect the play to be stellar, but the Queen sac is pretty cool. Happy New Year, all!!!