From the Bluesky TOS:
Bluesky Social is available as a desktop application at bsky.app and bsky.social (each a “Site”) and a mobile application (“Bluesky App” or “the App”).
…
These terms only apply to social networking that happens on Bluesky Social services, including the Sites and Bluesky App. If you’re using another social networking application on the AT Protocol that isn’t Bluesky Social (we call this a “Developer Application”), the developers of the other service will provide the terms and conditions that govern your experience.
So looks like the Bluesky TOS simply doesn’t apply. Create a developer application and give it whatever training-friendly TOS you want.
IMO smaller populations lead to a stronger echo chamber effect. I’ve definitely noticed that the echoness of Threadiverse communities is generally a lot higher than corresponding subreddits and I suspect the small size plays a major role.