The screenshot of the fighter beeing alone was taken right after the last capital died. The fighter did not get a duel, that is true, possibly because there still were a destroyer of wich we did not know the location, two fighters and a gunboat in the system. In that specific matter, I may remind you that SCRA fighters 2v1 a BAF snub in this very fight as well, conveniently not mentioned by you, yet no problem in my opinion. In groupfights there are situations where people get targeted by more than one person.
The battleship offering cover was asked not to open fire on snubs after that local message and held to its order.