I have no legitimate answer. However I have the theory that it might have to do with the properties on 3H+K. That's a fucked up move. i15 moves work. But yeah, sorry I don't have a concise answer.
I was trying a new tech shared by the community member Darkslay regarding "meaties" in doa (aka frame manipulation via force techs ) and tried it on ryu . For some reason , that rule doesn't apply in this situation . the 3(H+K) gives +16 BUT that 14 frame +1 is timing based and why ? Don't know.