The better translation in the OP makes it seem like Nintendo only mandated him to use character who is "very fresh", and it was Sakurai's choice to look for one in Three Houses. He doesn't know everything that's in production at Nintendo, so I guess he shouldn't be blamed too harshly for deciding on a Fire Emblem or a Pokémon character in that sort of situation. Maybe he could've chosen a third party character instead, but I imagine just working with Nintendo would be far easier since you're already in communication with them, don't need to negotiate all the rights stuff, and getting your hands on an unfinished version of the game would be easier than if he worked with a third party.