That's one of those things where since nobody really uses it the other ways, you'd have to pretty much explain in detail that you didn't mean a mother and daughter and it sort of defeats the purpose of using a specialized term. I think I have seen one series that made a joke using the potential use for oyakodon to include a father instead. I'm not sure it's brought up that often in series when it is the more common use to begin with, more of a thing in the fandoms I guess? Not that I'm faulting you for explaining the more extended use of it, I've done that on here before too. Just expanding more on why you had to say it was "technically" usable.