Also OAuth only handles auth and permissions and doesn't do anything for provided federated views of disparate data sources.
Also this isn't about identity either, you're really misunderstanding what this is about.
It is very much about identity. To use tangled you need to use ATProto and authenticate using ATProto – rather than using the existing open standard for authentication used by pretty much everyone at this point (missed opportunity to login to Tangled using GitHub). What's crazy is people still use the web to interact with tangled anyway.
It's like records are born to replicate for better or worse. They get downloaded immediately and you have no control over where they go after that. Anybody can tap into one of the firehoses spewing them all over the place. But they're all linked together and if links break it's because nobody kept a copy of that record.
Other file formats don't work quite the same way. A git repo is easy to clone and pull from, but things like call graphs are language-specific.
It seems hard to say what apps this sort of replication is right for.