[Tallguy]

It’s certainly possible that the ME-262 could have exceeded the Speed of Sound in a dive (though how it would have been recoverable is a major question). But aviation records require verification and as we say in Scuba diving, “If you didn’t get a picture, it didn’t happen.”

[Captain Walker]

But they acknowledge that the pilot most likely did break the sound barrier (and precede Yeager).

In order to keep Yeager (and the Americans, of course) on top of the Germans, they just changed the wording n the record book (adding, "in level flight") (as if that meant much to the pilot flying at the speed of sound).