This looks like a race condition: In rust-lang/miri#3399, I did bors r+, then I did a force push, then the tests started.

Commit rust-lang/miri@9dfd214 has been approved by RalfJung

Testing commit rust-lang/miri@00f700d with merge rust-lang/miri@bf1e82f...

Note how it is testing a different commit than what got approved! No idea how that is possible, I thought it would store in a database "commit X got approved" and then it will only ever test that commit.