There’s two points to note. First, maneuverability is not necessarily correlated with wartime kill performance. Tactics, roles, training, and assignments count for a lot more. Kill stats are not correlated with airframe performance or capability.
Take for example that the USAF F-4Es were mainly tasked with air to ground missions in Linebacker, replacing the departed F-105s. The USAF reserved the air to air MIGCAP mission for F-4Ds flown by well trained aviators & equipped with Combat Tree IFF interrogators. Obviously pilots ordered to engage enemy aircraft will log more kills then ones whose job is “bomb this target and go home”.
Further, US naval crews enjoyed a situational awareness advantage over their USAF counterparts. The North Vietnamese opposition knew well in advance when USAF strike packages were coming and from what direction. They planned accordingly. But US Navy Phantoms could enter North Vietnam from any direction on the compass, which drastically cut their GCI’s capability to vector MiGs for a hit and run pass. USN Phantoms were also not as fuel limited, which meant more engagement time vs USAF crews who had to balance kill opportunities with the pragmatic need to save fuel for flying hundreds of miles over hostile territory before reaching home base.
So, all that is to say that the F-4E’s kill statistics have no bearing on perceived superiority vs the F-4J.