You said "H8K2 basically a structural knock-off" which reads as a copy. I didn't say "inferior copy", just copy. The implication of those words are that the Japanese didn't create their own, they just copied the British. I will be blunt, as Mitsubishi and Nakajima engineers were in post war interviews, Japanese engines from before the start of the war were licensed copies, or derivatives thereof, of American and British engines. They most certainly did copy things, but they also created their own designs as well.
Yes, they do look similar, though IIRC the H8K is somewhat larger. They look similar as the basic form available for a large flying boat is significantly dictated by the "boat" portion of that and the hydrodynamics of taking it off of the water.
