I think it's possible for you both to be correct. The definition of "neutralized" could be taught to officers as "you are 10000% sure he is dead", which is only done by firing your entire magazine into them. So while not explicitly trained to empty a magazine, it could be taught implicitly. I get the impression there are lots of "gotchas" like this in police training. Evidence in many police shootings seems to suggest emptying their magazine is normal.