I agree that is what happens, but the privacy pages are a bit awkwardly worded. For "Private with Public Family Tree" (one slightly more restrictive than what Notables are set to), it says: "that relatives are visible if the relative also has a public family tree". Then what Notables is set to is "Private with Public Biography and Family Tree", which would also include the same. Based on this, I would expect all relatives to be visible with either of these privacy settings, but they are not.
The other key item is "Public Family Tree". If this actually means "green lock", which is one less secure than Private with Public Biography and Family Tree, then it would make some sense, as it would mean that no living person's relatives (spouses, children) unless they had passed away.
So we may need more clarification of this as the behavior is certain as if actual "Public" or "Open" would be required to be able to see these relationships. Of course, the other item we have to be careful about is that even if they are a Notable, they have to meet the qualifications to lift their privacy from Unlisted. If the one spouse is yellow privacy and the other is unlisted, then of course, we probably should not be discussing the unlisted person nor listing them in the bio other than as maybe a "unlisted Notable spouse".