If that's a head of household, then you surveil him - and the principals (individuals in the family/household) preserve privacy.
If every individual has agency, then every individual tends to get surveilled.
If you think about this from a marketing/sales POV, you want to understand the primary purchaser, not necessarily anyone else.
Approaching from another direction, how can I delegate surveillance of myself to another third party who interacts with the system? It's certainly possibly for specific aspects (eg nominee deeds, LLCs with professional managers, etc), but being able to do so in general is not possible (eg many counterparties won't accept interacting with an LLC and will demand to know the beneficial owners). Surveillance systems are fundamentally totalitarian in that they assert having in-depth knowledge about your existence, regardless of what you've actually leaked to them.
The way you would delegate surveillance of yourself to another party is to give everything you own to that party in exchange for the ability to live on their property and never interact with the rest of society. Giving up all agency does not look like creating some legal fictions, it looks like withdrawal from society.
I'm not sure I agree with grandparent's assessment, but I don't think these are the strongest arguments against it. I think a better argument would appeal to incidental surveillance: my car has no agency, and nobody is interested in tracking the car for its own sake, but it is surveilled as a way to watch me.
I don't disagree and I've been on both sides of such agent relationships. But I feel like we are ultimately bickering over framing, due to the original article's terrible framing that fails to address underlying causes. It's not so much that I disagree with the original comment as that I don't think it fosters actionable conclusions.
Performing mass surveillance doesn't cost that much, demonstrated by the popularity of collecting "big data" - ie "we'll find a use for this some day". Rather than saying that surveillers decide to only collect data on the subjects with agency (because doing so to everyone would cost too much), it's more productive to talk in terms of surveillees taking steps to prevent the surveillers from having access to that data in the first place. Like sure if I turn my phone off to prevent my location from being tracked, the phone company could technically dispatch a costly private investigator to follow me around until I turned it back on. But that's outside the scope of what we're practically discussing.