That story is often told but is generally considered apocryphal. There is too much wrong with it procedurally. It's funny, but not likely a conversation that actually happened.
Not saying it’s impossible that he made it up or embellished, but it seems likely that it actually happened.
I'm sure he wouldn't let the truth get in the way of a good story.
It's possibly a little too cute or maybe embellished, but there's nothing in it that sounds impossible or beyond plausibility.
For reference I have a pilot's license.
Unfortunately.
https://np.reddit.com/r/todayilearned/comments/8x5ndw/til_wh...
Also Brian Shul (the originator of this anecdote) and his RSO were the only SR71 crew removed from the program. There is a reason for that.
Off topic, but be sure to run Javascript on theaviationgeekclub.com or else the code that breaks your clipboard will fail to run.
[0] https://en.wikipedia.org/wiki/Brian_Shul
[1] https://theaviationgeekclub.com/sr-71-blackbird-pilot-tells-...
As to "not using the same freq", military aircraft have radios with knobs that turn. They can certainly monitor and talk on civilian frequencies if they see fit to do so, and they fly in and out of civilian airports regularly on ferry flights (not the SR-71 obviously, but I know for a fact F-18s do all the time, because I used to stand duty at a command that owned a bunch of them and we had to file reports on what airport they were at). If they can't talk on civilian frequencies, how would that work? And they fly through civilian ATC owned airspace, they absolutely have to talk to civilian ATC.
As to Shul being removed from the program, have never heard that -- I'm not likely to take the word of some random on the internet about it.
Related post: https://www.airlinepilotforums.com/archive/index.php/t-56350...
Even after the transatlantic world record "fastest air-breathing manned aircraft" flights in 1976? Especially if they were flying below the record speeds (depends on the exact numbers, going by wikipedia, the record was for approx. 1905 knots, which of course is lower than the figure in the story)?
(But, yeah, I've heard plenty of people, including other SR71 pilots in interviews, question the validity of Shul's stories)
The actual top speed might still be, if it is, it's probably because they don't actually know what it really is. There have been multiple pilots who have said they could pretty much keep giving it gas and it would keep going faster.