Yes. Mobile and desktop apps have much more data leakage because they can store more data for longer and have much more APIs to use. A mobile app provides 100x more detailed data with more persistence than a website ever could.

This is well understood by the adtech industry and is why so many websites push apps in the first place.

Historically I think you are right but I'm not so sure it's still the case.

Do you think an iPhone with the tracking blocker engaged is still a richer source of data than the web app on an iPhone? Facebook claims that Apple's privacy protections cost them $10 billion of revenue the first year.

Yes. Apple's changes have reduced tracking in both modalities but webapps are far more constricted by Safari than native apps.

Yes that is what he's saying. It's also the truth and the only reason every social media forced you to use the app.

No, that's not why. It's because it's hard to make a performant Facebook webapp with all the bells and whistles.

Yes.

When i close the webpage, that page is gone. It's not running in the background silently collecting data. With a properly configured browser (a few extensions, no third party cookies, or even separate containers), it doesn't have much data to gather in the first place.