Not a fan for a few reasons. Flathub (as far as I know) works on the app store model where developers offer their own builds to users, which is probably appealing to people coming from the Windows world who view distros as unnecessary middlemen, but in the GNU/Linux world the distro serves an important role as a sort of union of users; they make sure the software works in the distro environment, resolve breakages, and remove any anti-features placed in there by the upstream developers.
The sandboxing is annoying too, but understandable.
Despite this I will resort to a flatpak if I’m too lazy to figure out how to package something myself.
The point (as I see it) is not so much to stop scraping as it is to prevent bots from effectively DDOS-ing web services. As others have said ActivityPub content is public and there are ways to get it without slamming instances with scraper bots.