Karnak, ummm.... standard Bf109's have more MG's than Cannons, same with Yaks, and also the P38. Spits, A6Ms, and such have 50/50 in later varients, early varients had more MG's than cannons. About the only one I agree with you on is the Fw190.
Then your totally forgetting the P40, F4F, F6F, F4U, and the P51.
Look at the top ten or fifteen most common aircraft of WWII (by production) then calculate how many MG's were deployed and how many Cannon were deployed.
Its not a myth in the least.