Ok, I'll chime in here...in an official capacity...
I was the Director of the NJ Aviation Hall of Fame and Museum from 1997-2005. In that museum, we have most of the records from a company called Reaction Motors (of Denville, NJ). Reaction Motors claim to fame was XLR-11, a variable thrust liquid fuel rocket motor that was used in the X-1 (and also a 4-motor version in the X-15). Reaction Motors also developed the XLR-99, the world's first high-variable thrust rocket motor. Bell Aircraft's first X-1 test pilot was a gent named Chamlers Goodlin, aka 'Slick' Goodlin.
I knew the man personally and were good friends. Sadly, cancer took him in 2005, but, in several conversations, he related that HE piloted the X-1 beyond the sound barrier more than once. Slick made 26 flights in the X-1 before it was handed over the USAF. Because the X-1 was an Air Force project, that fact was kept under wraps.
It was determined that the official breaking of the sound barrier was to be done by the military as a way to show off to the world. Chalmers commented that because the media and the world were watching, they (Bell and the USAF) wanted to make sure that the sound barrier could indeed be broken without destroying the aircraft. In other words, it was a perfectly planned media event.
Now, take that for what its worth. Perhaps he was a man who felt jilted that someone else did and got the glory. Perhaps he's telling the truth. All I know, is that I had a signed photo of Goodlin hanging in my office, and there was no denying what the man accomplished.
Take it for what its worth.