The effect of pores is not an "open or shut" case either. (Sorry couldn't resist.)
I'm guessing here, but I suspect meat pores are the capillaries that wick meat moisture to the surface as the meat cooks. I can believe they shrink with cooking just because with less water you have less surface tension keeping pressure on the capillaries. But then again, less water in the capillaries means more room for smoke! (I love how I can convince myself of anything!)
And there are multiple mechanisms to making meat taste smoky too besides porosity. E.g. the water beading on the surface is effective at grabbing smoke and condensing out around it, just like a cloud raindrop forms by condensing around dust. As 1moreFord notes, that doesn't just stop at 120 or 170F. Then again I'd expect the effect to be more prominent in the early (cooler) part of the cook.
Still, I suspect porosity is a major driver. That's prob why pressure cooking with smoke is SOOO effective...the increased ambient pressure enlarges the pores. Similarly, I'd think vacuum-packing meat would shrink down the pores, and they might not snap back again when the bag is vented. Can anyone with one of those vacuum bag thingies comment as to whether vac-packed meat seems less likely to take smoke flavor when ultimately used?