Kev. you've got a great eye my friend. Those are indeed oak chips. And that color on the bird is from oak. One of my projects while the missus was away was to saw / split more post oak for the BIG smoker (AKA Locomotive Breath).
Those are chips from my chopping. I gathered a few handfuls and tossed em in the beer cooler ( by that time was empty).
The color was okay. But not as near as pretty as yours turned out.
You've got a good point about the rub on the skin diminishing the appearance. I look at mine, then yours and the difference is clear. b
It looks like Post/white oak, and a light application at that. Its why your cracks and crevices are lighter. Its a beautiful smoke job. Most have a heavy hand applying smoke. A light smoke is normally appreciated IMHO.
You did a really great job.