oh, that.
Well, most characters, if they double jump, will be just a little lower than Sonic. It's not enough time to jump, fastfall, and hit the spring - you'd have to have a stall-then-fall to pull that off.
Multi-jump characters will be considerably lower because multi-jumpers tend to have low jumps.
It's also the issue with the "have Metaknight chase you with Tornado and catch him with a grounded spring and force him into side-B" idea. If you're predictable, the Metaknight can just double jump, or even start a new tornado as soon as he hits the spring.
When I tried that against an MK that caught on, I noticed he'd only pull it off if I made the spring before he even started tornado (lol). But if he was already chasing me and I'd do it, then I'd be able to force him into a side-B.
So the issue is predictability.
either way, the Anthinus combo was never a combo in the first place lol