So, if it's not the official policy in an office, it is probably still grounds for action, since most offices expect a certain level of ethical behavior toward coworkers.
There are reasons why managers can't generally have relationships with a direct report. HR at my company forbids it.
That being said, perhaps this is a way to work around the normal pitfalls, where if there is a potential conflict, the person in question can be a "practical" manager, but perhaps not a "supervisory" manager. Those are horrible words for it, but I mean in that one manager would be actively overseeing the work, and the other would be a lower level of involvement check/balance against the former. It may be more manpower to do this, but it's generally how the engineering teams here work out anyway; that there are the engineers who have been here longer overseeing the new hires in the work, with a more uninvolved formal supervisory structure as well.
(This has other problems, I'll openly add, but has allowed for a situation like mine to exist, so it does make me look twice.)
Sorry for the essay, this ended up being a lot longer than I had originally intended.
Also certain organizations forbid higher ranking and lower ranking people to even hang out outside of work, develop close personal relationships, or even have about personal/non-work conversations. Many militaries operate this way. My sister also worked for an organization that had this policy.