Legendary Hero Event

I've seen a lot of claims that are like, "If you're trying for a specific hero, your chances are worse here than on any other banner." Can someone please explain that to me, without just saying 'go to a simulator'? How is it that having an 8% chance to summon a 5 star and only 1 of 3 options for each color 5 star is a lower chance that getting the 5 star you want when there's only a 6% chance(assuming them to be a focus hero) and about 20 other options per color the RNG could throw at you to ruin your day?