Well it isn't like they are inventing their own nomenclature either. Where are Jimi's scale books he wrote in his own modes? He didn't operate in those terms. He was very much like my cat, having an insinct for a formalized theory he does not know the formalized language for.

Is it understanding formal music theory? No, only if you stretch the definition of formal music theory to include what is definitely not formal music theory by any one's definition.