You seem to be confusing the promotional Gatchas (which exist purely to encourage impulse purchases) with the bonus rate for recently introduced kamihime in the Jewel and Premium Gatchas. This bonus rate does not apply across the board to kamihime for that element; it's simply a 5x increased probability that if you roll a kamihime of a given rarity, you'll get that particular kamihime instead of one of the others. Around September that 5x boost will be increased to 15x.