Not exactly, there are different clocks . And there is different phase jitter , other than msb femto 140 and Rockna femto 300 clock, I found other TCXO with 82fs and 75fs .
And msb galaxy clock is 7fs .....
So many many different clock with different phase jitter, and it is also determined by the where u start measuring , +-1hz or +-10hz....