popa: No he isn’t. The word nazir means “I am warned off” as we see later in the same halacha where the guy “nazirs” himself from dried figs. If he said “hareini nazir lchartzanim bilvad” you would have a point. (Not my own diyyuk. Comes from a rov who learns in MTJ).
HaLeivi: We don’t shecht on a roof (with exceptions) because things that look like idolatrous sacrifices become assur. This isn’t idolatrous, though it probably is sacrilegious 😛