If you need to self-host, self-host. Sourcehut is obviously not a replacement for that.
But, if not: It is different because Drew DeVault is scathingly anti-AI, and has a history of sticking to strong opinions (for better or worse). Seems like the best bet for off-premise source control if you are concerned about AI scraping and downtime.
Yeah, collaboration usually requires some sort of centralisation. Whether that is the LKML+git.kernel.org, gitlab.gnome.org, salsa.debian.org or Sourcehut, or GitHub. At least Sourcehut isn't completely proprietary and shoving AI down your throat at every possible chance. The same can be said for Codeberg and almost any GitLab CE, Gitea or Forgejo instance