Having read some of his in-depth posts on this topic, I believe John knows what he is talking about, however this paper does not go into the same level of depth (I suspect to cater to a broader audience).

In the paper he tries to answer your question by saying:

'Noise on the ground-plane of the DAC causes effective jitter in the DAC chip, which modulates the audio signal coming out of the DAC. Note that the actual clock signal does not change at all. It is how the clock circuit inside the DAC chip sees the clock signal that matters...

We have identified two primary external mechanisms—present in various digital interfaces—which can cause ground-plane noise on a DAC’s internal ground-plane: 1) Jitter carried through digital data and, 2) leakage current.'

In other words, noise introduced by external digital clocks can cause ground plane fluctuations within the DAC, which, in turn, causes jitter on the how the internal clock signal is read. Which is supported by what Meridian said a few years ago when launching their Anniversary Edition and the reason for redesigning the ID40 input card.

Prolific music listener / Hi-Fi addict!