I've received more replies to my queries from the authors of the Vital Smarts study. I've updated my post to reflect them (see the end of the post), beginning with these words, and inviting the authors to respond directly:
This just in on July 19, 2009: The person with whom I'm corresponding at Vital Smarts tells me that they employed "pathing," meaning that if someone indicated that they didn't participate in virtual teams in question 1...
For more, go to the end of the post.