Thanks Kijinki. Way over my head, but I appreciate the attempt.Draw on paper two horizontal lines connected by 45 degree transition. Let say, that level recognition point is in the middle of this transition. This will correspond to particular point (draw vertical line). Now, replace this 45 degree straight diagonal line with wobbly line - like sinewave (that’s added noise). Vertical point corresponding to midpoint will change. Vertical line (time) was shifted.
Imagine that you send digital stream producing 1kHz tone. If this digital stream shifts back and forth in time 60 times a second it will result on analog side of D/A conversion with 1kHz tone and two added tones at 940Hz and 1060Hz called sidebands. Amplitude of these sidebands will be proportional to amount of the shift. These sidebands are extremely small, but are still audible since they are not harmonically related to root frequency (in this case 1kHz). With many root frequencies (music) there will be many sidebands, resulting in added noise. This noise is present only when signal is present, so it is hard to measure it. In addition, this shift of the streamed data doesn’t have to be caused by one singular frequency, like 60Hz (correlated) but it might shift at multiple frequencies (uncorrelated).
Perfect transitions (like 0ns) will still have amplitude variations of the midpoint, but it won't change the time moment of level recognition (exact moment of transition). That way slower transitions are more likely to add noise induced jitter.