I'm skeptical of that claim but I'll take your word for it.
It would very much be an unusual exception, in that era and now. First flights rarely even raise the landing gear, let alone push the performance envelope. Flight testing programs are designed to be incremental to manage risk as well as learn things in a deliberate vs yolo way.
Rockets are really where you see the opposite being the norm, because it's hard to do a rocket launch half way.
