For measuring, sure but since we are at levels of inaudible differences it just isn't necessary at this time.
I agree on audibility, but there are also bragging rights
By that argument, the new Purifi amp isn't needed either. Many want it because of the excellence of it's measured performance regardless of whether or not that extra few dB is audible. Putting it out with anything less than a comparable buffer is doing it a disservice.
To be complete fair to Buckeye, they are two reasons to buy a 9040 based amp: 1) lower noise and distortion and 2) more power and stability on very difficult loads.
The choice of buffer topology does not affect point 2). At the same time, point 1) is obviously still achieved with a 1612-based buffer with respect to any implementation of a 1ET400A, 1ET7040A, NCoreX, or Nilai based power amp. But, yeah, it could be improved.