My guess ?
These two agents were paired together because of their proven hatred of Trump, their ‘skill sets’, their willingness to ‘do anything necessary’ and their ‘connections’. The ‘lovers’ story is just cover to explain why they were texting each other so much and often seen together.
I think you might be right. That was so possible, what you said. A mission in common is the only certainty in their connection. That number of texts would *need* a cover, for the embarrassment it should cause the FBI to otherwise explain them. They were two sharks proving a coup mentality. Yikes!