It’s better because PPA isn’t about targeting ads at all. It doesn’t share any browsing history, topics, or any information for ad targeting to advertisers at all. What it does do is provide a way for a website to tell your browser which ads are relevant to an action you take - for example on a checkout confirmation screen the site may tell your browser “here’s a list of ad IDs for the shop you just bought from”. Your browser then checks if it’s seen any of those ads, checking completely using local data that doesn’t leave the browser, then to an aggregator it reports which ads possibly led to your purchase. The aggregator increments a counter for each ad in its database and relays the totals to the advertiser. There are no unique identifiers or any information about your habits or interests involved.

When I initially heard about PPA I also thought it was related to FLoC / topics, but it has nothing to do with ad targeting or sharing information about habits / interests, it’s just a way to tell advertisers “Ad XYZ was effective and led to a sign up/purchase” without revealing who saw the ad or any personal information about them, just the total number of people.