It looks like aarch64-unknown-freebsd was available from the beta channel prior to the 1.97.0 release, and aarch64-unknown-freebsd build artifacts for 1.97.0 were uploaded to s3://rust-lang-ci2, but it seems not to have been included alongside the published release artifacts. The addition of a dist-aarch64-freebsd CI job was included in the 1.97.0 GitHub milestone. The proposal for promotion to tier 2 was accepted well ahead of the release, and the release build artifacts exist, so I'm confused as to why it's not installable as part of 1.97.0.
(This seemed an appropriate place for this comment but if it's better to open a separate topic for it, I can do that.)