I believe it’s an excerpt from a book called Sled Driver. As such, you have to wonder if it ever happened at all, or if it was there just to sell books
There is a another story in Sled Driver that goes along the same lines. Pilots requesting to fly at higher altitutes to show off. Some fighter joke request 50 or 60 thousand feet. He gets cleared and then the SR71 requests 80,000 the controller says and just how do you think your going to climb to 80,000? And the sled driver says “we want to descent to 80,000”.
One of the things that never gets reported is that there is a network of radio monitors manned by civilians that monitors many frequencies around Area 51. I have heard recordings of stuff they have captured and it is interesting to say the least. A few communications along the lines of this story.
I visit NAS Fallon on a regular basis, home of the Navy Top Gun school. I always have a scanner on and recording when we go out there. Record some strange stuff.
I tend to believe the OP. The speed the Blackbird was going was not close to the classified speed and is the declassified max speed of an F-15. Altitude - different story.