It appears that you and I are the only board members who have extensive missile experience.
Most likely. Most people can not be bothered to do any kind of research, so just believe whatever source they want to believe. That is likely why so much of the information you see people repeating in here are largely made up. They got it from some "news source", that is simply repeating what they read in some press release.
And if one applies some simple common sense, it should be obvious most of them are complete nonsense. Like the claims of being more "maneuverable" at hypersonic speeds. How maneuverable was the SR-71? The Space Shuttle? A Formula One car at over 200 miles per hour?
There is a direct link between maneuverability and speed, and they are inverse of each other. The faster something goes, the less maneuverable it actually is (other than in altitude). Sure, it can really dive faster, and maybe climb faster (primarily because of the speed it is already at). But they can not change direction very much or fast all all or they will break apart. And they can only maintain those kinds of speeds in the upper atmosphere where atmospheric density is low.
The SR-71 can reach amazing speeds, at 80,000 feet. Where atmospheric pressure is not the 1,000 millibars of sea level but at around 28 millibars. And even at those altitudes with such low pressure the outer hull would reach over 700 degrees F. If it tried that at say 35,000 feet (the altitude of most commercial airliners) the atmospheric density of over 230 millibars would cause it to burn up like a meteor. At closer to sea level, it would immediately suffer structural failure and break up.
I have been riding motorcycles for over four decades, and this can really be seen on a bike. At 5-10 mph in a parking lot, I am highly maneuverable. I can make circles easily within the length of the bike, and can do figure-8 turns in an area about 2.5 times the length of the bike. But as I increase in speed, the ability to maneuver is drastically reduced. To the point where over around 40 mph the ability to do much more than small changes in direction are about the limit. In other words, changing from one lane to another instead of a 90 degree turn to another direction.
Most of this are simply common sense things if you understand things like pressure, wind resistance, and Newton's Three Laws.