You know what matters, honey. Style Savvy brings something that Smash lacks: an unapologetically feminine non-combatant. I'm talking about a fun-loving, ovaries-to-the-wall, catwalk-strutting, pop music listening, handbag pummeling fashionista extraordinaire that would even make Lord Ghirahim cosplaying as Barbie blush.
In all seriousness, Style Savvy is solid and worth getting into. Some people like Soul Calibur 6 for its dress-up mode, for example, but it's got nothing on the size of Style Savvy's content. Plus, the devs behind Style Savvy made one of the best wrestling games of all time (No Mercy on the N64), and one of the good aspects about that game was its character creator mode, which was years ahead of its time.
In short, without knowing much about Style Savvy, it appeals to a demographic that Smash doesn't cater to (little girls), and her exposure would benefit Smash and vice versa. Plus, the Stylist is unique because she's from a freakin' fashion video game; there's nothing even remotely like that playable in Smash. There's so much to love. Moreover, she's from a first-party IP with no playable reps so far, is recent, relatively popular, and would be a great representative from the DS era (which lacks reps) that continued to make games after said era (4 games total and more to come, most likely). Personally, I love the art style; the characters are so cute, haha. So far, the series has 3 (catchy) songs featured in Smash Bros. in just 2 games. I think even Sakurai wants this to happen.