?? Why is the bottom/top dichotomy necessary here, it’s pretty clear they both fuck each other. Just because someone receives once doesn’t make them “a bottom,” most relationships (and most people) aren’t even like that.
I don't think it's "necessary" in any context, but it is fun to talk about. People like to speculate about characters' sexual proclivities and how they line up (or contrast) with their personalities.
Obviously fully realized human beings have many facets to them and a variety of dynamics in their relationships.But some people have pretty clear preferences and stick to those.