This all reminds of the thinking behind the specification that led to the development of the Defiant. The Air Ministry figured that modern bombers were so fast, fighters could only attack when the relative speeds between the two were about zero, and the fixed, forward-firing guns of standard fighters meant this could only be achieved by squatting on the tail of the bomber. Hence, the Defiant, which in the minds of the Air Ministry folk, could chose exactly what angle to attack the bomber. I guess they were proven wrong...
Oh, this also reminds me that some Japanese intercepters had fuselage-mounted cannon that fired obliquely, presumambly so they could attack from below/above their target while flying alongside. I think this was inspired by a Luftwaffe innovation??? Was this common?