Anything that changes the risetimes and falltimes of the output of the transport (i.e., the amount of time it takes the signal to change between its two voltage states), or that changes the amplitude or spectral characteristics of electrical noise that is riding on that signal, or that affects distortion of the signal waveform that will inevitably be present to at least a small degree, could conceivably end up affecting timing jitter at the point of D/A conversion in the separate DAC component. The degree of any such effects, if present at all, would certainly depend on the specific designs of the two components, and perhaps also on how they are interconnected and on how AC power is distributed to them (which in turn can affect ground loop-related noise).
But is it possible that breakin of the electrical and/or mechanical components in a transport could affect these characteristics of the output signal to an audibly significant degree? I don’t think any of us can answer that definitively, but I also don’t think the possibility can be categorically ruled out. On the other hand, though, it certainly seems possible, and in fact likely, that **some** reported findings of breakin phenomena are due to unrelated changes in the system (such as ongoing aging or breakin of other components), or in its environment (such as changes in AC line voltage or noise characteristics, or in ambient temperature). Not to mention the possibility of inaccurate recollection.
Personally, I don’t use a separate transport so I can’t speak from experience. And in any event I would by no means extrapolate experience with a particular transport/DAC combination to other designs and other systems. But given the foregoing my expectation is that the truth lies somewhere in the middle ground between the opposing points of view that tend to be expressed on such matters. In other words, IMO the answer to the original question is a definite "maybe." :-)
JMHO. Regards,
-- Al