I suspect that the real reason the Org wants needs to keep ministry/door-to-door records has do to with retaining it's "charity" status.
They don't do soup kitchens, clothing drives, or the like, so "preaching the gospel" is their only real qualification; therefore, they need clear, unambiguous records in case they're ever audited by federal revenue agencies...
...because - if I'm right - the Org's financial survival has become dependent on its tax-exemption.