This comes up from time to time. MiaB supports older TLS versions because some clients still use it. MiaB prioritizes higher versions. If they were to disable older versions, it would break and leave some unhappy customers.
As for TLS 1.3, it will probably appear in the next major release. Maybe. I don’t see any mentions in Github.
Are there plans to remove some of the less secure cypher suites? Not disabling TLS1 completely for legacy support reasons, but removing 3DES for example?