Importance of clocking

What about the clock accuracy releasing the buffer, then?

I specifically addressed this in my first message. You literally can’t avoid jitter without buffering, but in the case of a network stream from outside the home having more "clocking" at upstream devices, without buffers doesn’t help you because the original stream has huge amounts of packet to packet variation (huge relative to an audio or video playback). In fact you can end up in a situation where your original DAC’s jitter is worse because there’s an upstream "reclocker" that has so much jitter it’s forcing the downstream DAC to misbehave.

The best possible place to put a fancy clock is less than an inch away from the DAC. External clocks are used to produce music in the cases of multiple DAC’s or streams happening at once, as in the case multi track recordings and mix-downs. Those clocks do NOT however dejitter anything.

In my setup both the Etherregen on Ethernet and the UIP on USB can run on their own clocks or supported by the 10m clock. The difference in sound quality isn‘t subtle and that is what my post was about. It seems you are arguing from first principles rather than own experience

What about the clock accuracy releasing the buffer, then?
 

It is internal DAC’s clock that is unaffected by any external activity (asynchronous).  DAC uses this clock to take sample of the data from the buffer and convert it to voltage at exact intervals.

It does not matter if this internal clock is inaccurate.  We cannot detect if music plays tiny fraction of percent slower or faster, but we can hear when this clock is jittery because uneven D/A conversions intervals add additional frequencies to audio signal.    We likely cannot hear jitter artifacts when jitter is below about 50ps (peak to peak) so names like “femtosecond clock” are nonsense.
 

Releasing a dirty stream to the D/A increases its processing load leading to distortion. This applies to all dacs but is particularly noxious when using upsampling. That‘s why reclocking the data before conversion has benefits. And by the way, excessive buffering leads to latency while underutilized buffers need empty packets fill-in, again increasing the processing requirement on the D/A converter. Be that as it may and as stated previously: in my setup the benefits of external master clocks is easily demonstrable

Releasing a dirty stream to the D/A increases its processing

No it doesn’t, latency has nothing to do with it and buffers are never “underutilized” because of back signaling.

Perhaps example will help:

Worker (DAC) has to place items on conveyer belt (D/A Converter) of some machine in exactly one second spacing, but another worker (computer) hands them too slow or too fast creating uneven space between them.  Remedy for that would be shelf with many items on it (buffer).  One worker adds bunch of them (frame) to the shelf every so often and the other places items on conveyer belt in even intervals, yelling back “get more (or less) next time” to keep decent amount of them on the shelf (back signaling).