If I’m going to smoke, I do it before SV, and have found that I can actually cut back on length of the smoke because I feel it somewhat intensifies during the SV process.
That's interesting. I've noticed that some spices seem to disappear when SVd and others seem to intensify as you say the smoke does. This could be a great blind taste test of beef smoked before and after SV.
I think the reasoning is that the only thing that will penetrate the meat structure is salt when it comes to seasoning, smoke particles are small, they will go through the pores in the plastic bags. I have noticed when I smoke first that the water will have an off color and smoke smell to it. As for the seasonings, it seems most of it get washed off in the bag as the meat releases moisture, it makes a nice flavored sauce if you are into sauces.
I believe sugar may penetrate also if mixed in a brine, other seasoning and flavors seem to be only surface treatment and if you are one to wash off the brine you pretty much wash away most of the flavors you put in it from the start.
These are my thoughts, from my experiments, no science was harmed here.