This is just you buying the ad slot instead of the advertiser. Why should it be any different for the website's income?
If anything, more entities bidding for the ad means the prices can go higher and the website gets more money (though I imagine any difference here would be undetectable).
> Why should it be any different for the website's income?
Because the point is that a lot of people who block ads, don't actually like advertising. I would hazard a guess that they want to support websites, but they don't want to support advertising companies, and validate their business.
If anything, more entities bidding for the ad means the prices can go higher and the website gets more money (though I imagine any difference here would be undetectable).