I would expect a spouse to be considered a relative.
The public profile view is geared to the viewer, most of whom will not be relatives, not those on the Trusted List.
Example - I created a profile for my first father-in-law. I am, therefore, the Profile Manager - and, by default, on the Trusted List. I know who his wife was - because I also created a profile for her.
When I view either of those profiles using the PUBLIC view, (using the father-in-law for this example) all I see is :
Son of [father unknown] and (redacted)
Father of (redacted)
No wife. It's as though -- in the public view -- she doesn't exist.
If I switch back to the normal view for me as PM, I see everything I have added, including the spouse.
This is not a bug. It is working as it was designed to do.
If you want the spouse to show on public view, consider how much of the biography, etc, you wish known to the casual viewer, and lower the privacy level to green - or open.