In think either our idea of "by definition" or something else differs.

Viewers get ads matching their interests, as proven by the fact that they are on a related website. I don't see how that isn't "matching ads to viewers"?

I think maybe the problem with the comment was that it started with "I think that’s incorrect" but it reads like a non sequitur. The comment to which yours was replying was claiming that matching ads to viewers is itself a privacy violation but your point seems to have been that it – matching ads to viewers – is unnecessary, which, altho related, is a different point and doesn't follow from you thinking that the other commenter's point is "incorrect".

I think you're right in that "site content" is a good-enough proxy for users/viewers/targets for advertising, tho I also readily understand why advertisers would always like more info with which to target their ads.