I guess they're legit instrumentals, since there are no backing vocals, they're in very high quality and I'm hearing all kinds of instruments in different way since Billie's vocals masks some instruments too well; just listen Kill the DJ and Makeout Party for example and skip straight to post-solo where bass sounds insane!
Now if only we had multitracks.. damn I'd listen that guitar only tracks for dayssssssss.
Oh, Let Yourself Go is certified banger and it's sad that The Boys don't play it anymore :(((