There is a difference between what others users see and what the post owner sees when a question is closed.
For example, when a question is closed as a duplicate users see1:
Some community members have associated this post with a similar question.
While the post owner sees1:
Your post has been associated with a similar question. If this question doesn’t resolve your question, ask a new one.
For community specific reasons, the list of guidance markdown can be pulled fairly easily through SEDE. For example, Stack Overflow's post owner vs public guidance
But there doesn't seem to be (or at least I can't find) anywhere in SEDE or on MSE a complete list of the current guidance for the network-wide/universal closure reasons.
Is there such a list somewhere (e.g. in the help center, mod tools, on MSE, etc.) or a way to access this information through SEDE?
1 There is variation based on whether a the question was closed single handedly or by multiple users, and variation if it was closed with a single duplicate target or multiple (but not really the primary point of this question)