Apple still has a lot of extra measures in place to work with carriers, they just do it ahead of announcing updates instead of dropping the code like Google does and then waiting for everyone to fix it for their equipment.

From my recall, Apple actually has a "Verizon team" that works on ensuring iOS updates meet all of Verizon's certification requirements for release ahead of announcement, which is why Apple software updates never suffer that terrible additional wait Android updates have before they end up on Verizon phones.