Looks silly, but by any chance, have you tried to stop the server, clear the felix cache, start again? I don’t believe it’s a likely cause, but who knows?
Otherwise we could start to figure out what you and I are doing differently.
This is what I did:
Unzip 7.3.
Start without any configuration change (e.g : embedded DS repo)
Spin up my existing MSSQL server (Docker image), drop existing sync.json and provisioner file, reconciliation from MSSQL to managed Ok
Then checked the reverse mapping Ok (which has a property mapping from accountStatus → boolean in MSSQL with the transform script)
Then created a custom managed type, establish mapping between user and custom type, with same transform script. Implicit sync Ok, ACTIVE and INACTIVE correctly transposed to false and true.