That was my theory as well, Ryu has better, faster normals than Spencer and that gives him the edge at the start of the round against Spencer. Ryu also has his Hurricane kick hyper that can be used to kick Vergil out of his Spiral Swords along with his other invincible specials. Plus all of those characters are great whiff punishers, ideal for taking on Vergil. There is also the Wesker DHC counter hyper in case Justin gets too Bionic Arm happy. And of course the point that was brought up that Arrows > Cart but not Tatsu.
I don't think it was a great counter team more so that it was to throw off Justin and his game plan against ChrisG. It was high level counter meta/mind games going on there.