Yup. Build and Specialty phases are not the time to start reducing carbs and calories. Do that in Base.
I just finished SSB1+2 where I added a 2+hr fasted endurance ride every Sunday. Heading into Sustained Power Build I will continue to do the prescribed Sunday ride fasted, although these will be Tempo and SS workouts so not the optimum zones for fat adaptation but every little bit helps (and I have yet to pass out on the trainer!).
Good luck!