As I understand it, it refers to using meet.jitsi.si, not "another service" someone might provide by downloading the Jitsi software and running it on their own server.
Please correct me if I'm wrong since this would give me cause to reconsider running a Jitsi server.
The guys at 8x8 may be well intentioned, but their lawyers have done their best to not give the customer any basis to sue the company in any foreseeable circumstances. That is what company lawyers do, for better or worse.
Regardless, it appears that at present time jitsi is not including AI training in their service, and there is no explicit carve-out in their terms for AI training. However, by article 2 they do have the right to store user content, which might become a problem in the future.