I finally decided to overcome my fear of colorwork. Things were going well. Sure, I was probably going to run out of yarn (the danger of using leftovers) and I had some twisted stitches (must make sure to wrap the yarn in the right direction when anchoring the main color), but overall, I was very pleased.
Pretty bird design, the colors are working out, everything is reasonably even and likely to get more even with blocking. So I decide to try on the sock.
Yeah. That sock is not going over my heel, ever.
Moral of the story: yes, stranded colorwork is in fact less stretchy than regular knitting. Rrrrrip!