Calling him friend in narration was politeness?
Whatever, a social link does not start with friendship anyway, and a magus like Tokiomi likely wouldn't think of Minato as a friend until around level five, and wouldn't trust him fully till level eight or nine.
To put it simply, the ten levels of a social link cover the entire range between "New aquaintance who I may speak with again" and "Super best friends forever nothing will break us apart so don't even try".
Then again, this is Tokiomi...