Someone commented about the privacy concerns of monitoring sewage for drugs in the US, and were downvoted heavily. No theory is truly tin-foil in our world it’s beginning to seem.
I think there were objections about the feasibility and precision of these methods, when in reality those concerns just don't matter at all.
Raided the wrong house/neighborhood? I doubt the victim could do anything tangible about it. Even better, this is another tool in the box of vague reasons to search a place that can be just made up.