Can't use a fine grained token to the merge-upstream endpoint

[kaltepeter]

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Bug

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https://docs.github.com/en/rest/branches/branches?apiVersion=2022-11-28#sync-a-fork-branch-with-the-upstream-repository says it supports fine-grained tokens with the write permission.

• I granted write for contents on the two repos I cared about.
• I made the org where the fork resides the owner
• the organization requires SSO
• the user has access to both the private upstream and the forked private repository

My exact request works with a classic token with: read:org, repo and SSO-enabled

I received a 403:

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