The term 'descent' IMHO is misleading. Most planned continuos descents are done at idle. The flameout protection is much less than at high power. Also the introduction of heated air at idle power has less effect on engine power & efficiency. However, IMHO, if you are doing a short descent in say V/S 1000fpm and thus at about 80% of CRZ power you should not need EAI if >-40SAT and in cloud. You are using what would be a CRZ power for a lower FL even though you are descending. It a debatable point, but one where I believe the thinking pilot can read between the lines of the Boeing SOP and understand the reason for what they wrote and adjust their operation with airmanship.