It may be that the derate section of the AFM contains cert. data for anti-skid inoperative; this may be the case of the airplane originally cert. with early model engines, and later with uprated engines. In that case, flying to the earlier thrust rating is treated as a derate of the later engine model.
(Example: A300B2/B4 and DC-10-30 originally cert. with CF6-50A engines, later uprated to -50C, -50C2 etc. The -50A AFM chapter is still available as a derate to later engines.)
