there is actually a book about this fallacy. It’s only SLIGHTLY more likely that a traveling alien race would have non-ballistic weapons than not having it in the grand scheme of things. The primary requirement for space travel is resource dedication, and a pacified world wouldn’t need to continue advancing weapon tech. Therefore it’s plausible that a civilization stopped building weapon tech because it united early on, and without war to drive it it fell greatly behind other tech. Then, as they invade other worlds, whose species either don’t exist at all or are so primitive they can barely be called intelligent they never need to advance their mil tech. So when they ‘invade’ earth they do it with essentially futuristic cold war tech (in the middle of world war 2) so they have hover fighter jets, but still use basic radar chemical weapons.