Huh. This is actually a better idea of a whirlwind shield passive effect than what CloneFighter did. No offense to them if they read this.
Though they made the shield attempt to save you from a pit, this is just a slowfall. I'm gonna assume this works in a similar manner since I haven't used it yet.
EDIT: Okay, I tested it out, and it works just as intended. Funnily enough, this will work simultaneously with CloneFighter's Whirlwind Passive mod, as it'll save you from a bottomless pit (or at least attempt to), and you'll fall slowly, too. I'm not gonna leave a review, but I will give this mod 4 out of 5 stars. Only thing I have to say is that SRB1's Whirlwind Shield slowfall is a little better since it makes you fall slower, basically allowing you to glide through a couple enemies or hazards even without playing as Knuckles since he can already glide. But you tried, I'll give you points for that.