Sure, the Brits broke the sound barrier first as Geoffrey de Havilland did a power dive into the mud in 1946. All Yeager did was control his aircraft in supersonic flight and land alive.
Just as with first ascent mountaineering, a necessary condition for being considered “first” as a respectable accomplishment is to fully complete the action and return alive. Leigh and Mallory ***might*** have made it to the summit of Everest but they did not return alive and so it should not (in the eyes of sane people) count as a “first ascent”....