I see. But I guess you meant stress tests, because we are running integration test in CI which is more than unit tests.
Current release process is not performing stress test on MySQL/Postgres. But Cadence team is moving to sharded MySQL so it will come soon.
I do see the value you are pointing out, it’s great to hear that Temporal are performing all stress tests on MySQL/Postgres persistences. Even though it’s a thin layer, there could be changes that something unknown until we run into the scalability/perf issues. 
btw the bug is not related to persistence layer. It’s an edge case that we don’t have unit/integ test covered. It was also broken for Cassandra but most people are not aware of. Temporal doesn’t have the issue because the refactoring you did has removed the fields that could caused it.