With all the shitstorming output concentrated on discussing the 'Fairy-SE VS Dragon' frontier, next to nothing is discussed about further SE potential of the new type that was supposedly 'leaked' by Pokebeach.

According to this source, Fairy is also SE against Dark and Fighting types, while Psychic and Fire types receive only half of damage from fairy attacks.

How likely is this rumour to be true?

How will these hypothetical advantages affect the pokemon from dark or fighting type?