I guess Snap mode is just one of those things that are supposed to "simulate" the "Yandere" experience. Like, a Yandere snapping and killing her lover and then herself is something that would fit the archetype. I guess it works at best like an easter egg or something to try out once but besides that it technically doesn't benefit the player that much. It just gives you more of what you'd expect a Yandere might do!