Great points! Two thoughts:
1) I like your differentiation between zero-party data and declared data, which I never thought of. I suspect, though, that this is a smarter than average interpretation. In digital advertising circles my feeling is that the "zero-party" name was created as a marketing stunt to rebrand "declared data" and that now it will be almost impossible to fine tune the meaning.
2) I fear that such an application of legitimate interest in digital advertising will open the gates to systematic and widespread abuse. Happy to change my mind, though.
I know, I have become very cynical. But I love the article and the aim towards excellence, which we should all pursue.