It appears that under their system all forks belong to same repo (I imagine they just make _fork/<forkname> ref under git when there is something forked off mai

It appears that under their system all forks belong to same repo (I imagine they just make _fork/<forkname> ref under git when there is something forked off main repo) presumably to save on storage. And so accessing a single commit doesn't really care about origin(as finding to which branch(es) commit belongs would be a lot of work)