This is a change, so maybe it was correct when written but is no longer correct. All GGLs used to be able to pre-book spa arrangements at 28-days out, regardless of class of travel or if they were CCR card holders, as long as they were traveling long-haul. That changed maybe two (?) years ago. Now it is only confirmed First ticket holders, regardless of status, who can attempt* to book early - everyone else who is otherwise eligible for a spa treatment will have to try their luck on the day-of-departure.

*attempt to: just holding a First Class ticket does not guarantee that you will get an appointment. Even when calling or emailing exactly 28 days out, I'm only around 30% of the time able to successfully secure an advance booking. My personal opinion is that BA have no intention of actually following through with providing the service and have removed all investment from the offering, but for competitive reasons they need to advertise that it's offered. Similar to the lottery claiming to have loads of millionaires, your chances of becoming one are slim eve with a ticket!