effectively enough to get a good count...especially when it comes to the situations I noted. Note in the 2020 Census document I linked that census takers often go back up to six times to get needed information at housing units...and the expectation was that nearly 56 million households would need follow up. No way a Postal worker is going to be able to do that...and still fulfill their existing job description.
Not saying this approach would involve "Malice Aforethought", but given that large cities with many apartment complexes are often found in Democratic localities and states, the GOP might not worry about "Under Counting" the residents there.
Link: https://www.census.gov/newsroom/press-releases/2020/door-to-door-visits-begin-nationwide.html