On the potential for an interpretation remaining open for a court or government to claim that if it is only to certain households it's not part of the general census because it's not found in the law as opposed to it being at the discretion of the chief statistician, we're attempting to close off something for potential future court challenges around the mandatory nature of the survey of households and the long-form census.
I know that in practice, the statistician can say this is mandatory. In practice, some sections can be seen as being part of the general survey even though they go only to certain households. The reality of the threat is that there could be a future interpretation by the court to say that the act doesn't specifically say that questions that go to only some people by a different method are somehow still part of the general survey.