I’m reading through the WordPress core and noticed that the update_core transient is fetched with get_site_transient().

What is the difference between get_site_transient() and get_transient()?

If I had seen this somewhere else, I’d have thought: “well… this is to get a transient for a specific site in multisite.“

But if this is used for update_core, that thought does not make sense, since the core is one ond only one, even in a multisite.

Did I read the official documentation?

Of course, but it doesn’t really clarify it.