I have not contacted Mike Moffet via Head-fi web site to ask why he does not use a clock, but I do not have any concerns about Schitt DACs supporting a clock.
dCS:
"In a dCS system, the DAC can act as the system master clock, but listening tests have shown that there is no substitute for a dedicated high quality master clock. dCS pioneered the use of external clocks in digital audio systems and this clocking technology has been continually refined so that our latest multi-stage Phase-Locked-Loop (PLL) system sets world-beating standards for accuracy and control of troublesome jitter from the incoming audio stream.
MSB:
"Why are external clocks sub-optimal for digital audio?
A clock signal is a fast moving precision electrical signal and is extremely sensitive to added noise or distortion. Each time it’s buffered or transmitted, a portion of its precision is lost. Even if a small amount of noise couples into the clocks, jitter will increase dramatically. It might still be an accurate clock, but accuracy is of little performance benefit to digital audio. A clock sent over an ultra-high quality cable will still increase its jitter considerably. The best solution is to create the lowest jitter clock as close to the DAC as possible.
You could figure out who’s telling the truth and who’s trying to sell more goofboxes and wires...
M. Moffat + J. Stoddard know their stuff and happen to make honest things. No goofboxes and wires will be peddled by them.