As a (recent) former military pilot, I think your intuition is generally correct for the modern era. Our planned routes and maneuvers and flight conditions were

As a (recent) former military pilot, I think your intuition is generally correct for the modern era. Our planned routes and maneuvers and flight conditions were all annotated on a formal risk assessment which had to be briefed and approved by the appropriate command authority before we completed any other steps of the pre-flight routine. And crews did not deviate from that plan. Getting briefed and approved for something very different over the radio while in-flight, especially with sketchy weather conditions, probably would not happen. With that said, I've read several books about military aviation in the Vietnam era, and I compiled a long list of things that would "never happen" today. The difference shows up in the number of fatal mishaps over the years. The US Army lost more helicopters in Vietnam than it has today in its entire fleet.