Howdy all,
Brave intentionally disables these features because inputs from these motion sensors can be used to track users across the web without their consent. When we raised these concerns with the Chromium team in the W3C (around the relevant specs) they did not mention any immediate plans to address. Until their implementation in Chromium is modified so that they’re compatable with Brave’s privacy goals, we expect to keep them disabled (though we’ve discussed, but have no immediate plans to, allow advanced users to re-enable them through brave://flags. The main constraint here is competing demands on engineer time).
You might find these papers of interest if you’re interested in learning more on the topic. They are just a few in this area:
https://dl.acm.org/doi/pdf/10.1145/3243734.3243860
I hope this helps