It could also be a services counter, where they provide pool towels, life vests, mask and snorkels, things like that similar to Eb and Flos at Vero. At Eb and Flos, they have sign up for activities there, and rent videos. There is also a sauna and massage room.
Restrooms and locker rooms consistent with a pool area make sense, and provide members the opportunity to swim and change into dry clothes the day they arrive or are checking out like the other resorts. It's nice to know that if you arrive early before your room is ready, you can take a shower in the locker room and then jump in the pool until your room is available.