Yes for me at least JFK has been as bad as T5. The staff at T5 have always been genuinely apologetic, but at JFK they just appeared utterly disinterested and often quite rude. Admittedly F passengers are now allowed to pre-book treatments, but I still believe this is on a trial basis. I've not traveled in F since this improvement.

When I've quizzed staff at T5 about the lack of availability they have admitted that there is often a long line of transfer passengers waiting to book treatments as soon as the spa opens, so they are effectively running behind schedule as soon as they start.