If you actually checked the main site or read any of the other posts, you would see that the main site is incorrect about this.
I'm wondering if Feint does double damage if the opponent uses Protect/Detect, if it also does damage if the opponent doesn't use Protect/Detect and if it hits through a Substitute (Pokémon Stadium 2 classified it as the same type of move as Protect and Detect).
Because 50 BP does seem a bit low for an attack like this.