In game development, nothing "game breaking" will be changed in the course of a week if not spotted till reviewer code is launched.
The process of changing something that "game breaking" would result in a delay anyway.
This is just Bethesda/ZeniMax being grade A ***** or they just believed in their product.
It is more likely they tried negotiating for paid reviews but nobody agreed or just simply cannot be bothered with hassle of review copies seeing as nowadays it has zero impact on sales.