Since the F-4 was built as an interceptor, and some of this discussion gets into the pros and cons of a turning dog fight, it is interesting to see why people take the positions they do. My only data points on dog fighting of this era is from USN and USMC pilots who were 'Nam experienced, and whose general approach was to use to one's energy advantage and NOT get into an energy bleeding turning fight: going vertical was a way to get the advantage. (Best briefing I saw on that was by a Major named George Stuart, call sign "Smut." )
A signal advantage of the MiG-21 and F-5E (an aggressor used in fighter training with a similar performance envelope to MiG-21) in a turning fight was small visual signature: as Manfred von Richtoffen might point out, who sees the other first has an edge in a dog fight.
It's nearly 50 years later and the BVR RoE has been used ... how often?
I'd need to dig up some notes from a few years ago, but IIRC the IAF used that sort of RoE during the turkey shoot over the Bekaa Valley.
Question for thought: at what point will the "Western" RoE permit the use of all of the very expensive kit that makes a BVR engagement an air-to-air advantage?
A question worth asking, but one we can't answer here.