3rd Gen Counter to counter and mirror coat

I just realized this the other day when I was battling my wife. The very first time I tried to use mirror coat on her Tyranitar because I knew she would use crunch. Good right? But then you learn that because it's psychic type and Tyranitar is dark type that it doesn't affect him at all.. YET MIRROR COAT'S TYPE DOESN'T DO SUPER EFFECTIVE HITS ON OTHER TYPES?
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Why would that suddenly matter? And I'm sure if a ghost type used a ghost type move and attacked me and I used counter- the same thing would probably happen but that can probably be fixed with foresight. What are your thoughts on this nonsense?

Yeah, it sounds strange but it´s true. That means on Sableye both, Counter and Mirror Coat, don´t work.