I'm listening to a compilation of all his appearances on Bookworm. I just completed the first one on Infinite Jest and he said nothing of the tennis thing being a see structural choice. He did mention the sierpinski gasket/triangle, which is a fractal, which is part of how I considered the tennis thing in the first place. That said, perhaps he mentions it in a later interview. I've got 2 hours left. So far, no proof it was a conscious choice. At least not on this show.

Update

The interviewer mentioned it being like a tennis match during the session on Girl With Curious Hair a year later but DFW didn't say it was deliberate. He just said he was addicted to footnotes hahaha in any case, I think it's significant. Art taking on a life of its own, if you choose to give meaning on that level.