>>45869901It's because of mistranslation.
Dark is "Evil", it's dirty tricks, dishonourouable fighting, it is good against psychic on the basis that it distracts psychic which requires time and focus with cheap shots.
>You are sleepy, so sleep->[slaps psychic's face out of nowhere]Like that kind of thing. Bug types too, can't focus if there's a fly buzzing about.
That's my take anyway.
