You're right, I may have misinterpreted what tptacek said: he said he was using LLMs and that he was using Math Academy but I interpreted that as "Math Academy includes LLM features" - actually it's equally likely he's using Math Academy and having LLMs tutor him on the side.
I asked Google if MA does LLM tutoring and got back this answer:
> Math Academy does not offer Large Language Model (LLM) tutoring. While the company advertises itself as "AI-powered," this is in reference to a machine-learning-based adaptive learning system, not an interactive LLM tutor.
And here is a HN comment that indicates LLMs are a complement to MA, not part of it: https://news.ycombinator.com/item?id=43281240