These jitter measurements are mildly interesting. Low jitter measured one way is not an end-all, otherwise a few picoseconds of jitter would be all we need and no other products would compete. Not the case.
I use a completely different direct method of measuring jitter, which requires more expensive equipment. I think this method correlates more accurately to sound quality.
I'm planning to use this method to measure the Pi as well as my own renderer. Unfortunately, they don't allow posting of photos here.
Steve N.
Empirical Audio