I don't know exactly what an F5 sounds like, but I think I get your point and feel the same way.
There's also sections in the second verse where I wish she would stick to the melody of the song rather than chopping it up. "Cause I'm the... chick who's/You're the... medicine" idk, it just bothers me, makes it hard to sing along to.
I tried humming it myself to see where the proper note would hit and while looking for references, I came to the conclusion it was an F5, which is an amazingly high belt. I could be wrong, but it sounded like the right note she would need to hit to my ears. The one she belts is rather low and saps some of the release I was anticipating.
I agree with the chopped melody. I had already committed to the iTunes performance, but I suppose it wasn't so bad after hearing that LQ leak of that specific section. It does delay the rhythm a bit, but I'm surprised it hasn't bothered me enough to really dislike to track as I love so many other additions.
One thing I'll say is that I really dislike how they muted/muddied her voice. A lot of what gave them a nice touch was how she handled them live. I suppose this means I'll look forward to live performances of them, but Artpop will forever remain exclusively iTunes festival for me.