@louis I don't think this is recording anything identifiable about the search. Just timings, counts, etc. See https://github.com/mastodon/mastodon/pull/30350.
Furthermore, Otel doesn't by itself share anything with third parties. It's quite common to pipe it into a local monitoring solution. This data can be invaluable for keeping a service running.
This could be extended and configured for evil, but looks useful as it stands.