I would suspect that if you had a lower jitter source to the Shiit DAC to start with, there would be an obvious difference between the OPPO and the Shiit DAC.Perhaps. Logically what you are stating does makes sense.
I've read a quite a bit of information about transports here on Agon, and like much of everything else there is some disagreement, however, in this regard. In my particular case, besides the level of contentment I already have with the sound of my system, I am (for now) electing to side with the camp that would argue that any high-end DAC that purportedly has jitter control, reclocking and so forth will employ those functions regardless of how "clean" or "dirty" the incoming signal is to begin with.
So, I'm "relying" on the Yggdrasil to essentially "do its job" and what I believe I paid for, which is to correct the jitter, irrespective of how low or high it is to begin with.