Let's see: Gord wants Terry to sit because he is significantly taller than Gord. There is a picture of Gord, Rick Haynes and Red Shea standing side-by-side. Red is significantly shorter than Gord, but sat when he played anyway. I've watched bands where everyone but the drummer, keyboard player and steel player were standing, and it's quite distracting. From personal experience, I know that sitting while playing gives the player a much better focus on his instrument. Having everyone else sit makes Gord the "focal point" (he said this in an interview) for the audience to watch.
------------------
|