^^^^^In answer to your questions to me. Though I have no idea of cost per unit difference, obviously nitrile is less expensive to produce than silicone. However when used for the recommend oci/fci noted previously, nitrile generally should function as designed. Fwiw, GM ACDelco use nitrile adbv in thier factory and over the counter filters.
As for nitrile never being as flexible, don't know could be. The main advantage to silicone is it maintains it's pliabilty/flexibility over a longer period of time, thus making them a better match for extended oci/fci's.
As for all top filters using silicone, that would eliminate
Donaldson and Fleetguard synthetic offerings, and the elusive
ACDelco UltraGuard (UPF) synthetic. 'Reading this board' many members would consider them to be top tier filters.
As for the topic'd Nissan OEM, no particular fan. But as noted in my first post I find the OP's newer made in Mexico filter construction preferable to the previous made in China filter.
All that said, if having/using a silicone adbv makes one more confident then that's what they should use.