It can't be Sonic because springs don't bait approaches.
False. After Sonic springs he can't use any of his B moves, so Sonic will be approached from below; he has little defense below him, since Dair is so predictable and punishable.
Also, Captain Falcon can jab him out of spindash and U-air/U-tilt most of his aerial approaches, so it can't be him.
Every character can interrupt Sonic's spindash, which is why it has to be heavily mixed up (cancelling, opportunism, etc.) for it to be used as an approach. Sonic's fantastic recovery and aerials give him an easy time gimping Falcon, and Sonic is one of the few that outpaces him, amirite!?
Let me go through the hint more carefully,
since at least someone does this every week
This character is underestimated by many players, but in the right hands can give characters like Captain Falcon trouble. Sonic has been underestimated since day 1, many still claim he's bottom tier, partly because his best matchups are against low-tiers like C.Falcon.
With approaches that can be shielded or dodged, Which is why his spin-dashes are so difficult to use well as an approach.
this character can sometimes approach through the air. Definitely, Sonic's aerials are great but his aerial speed is not as good as his ground speed, which is why the hint says "sometimes"; you have to mix up both approaches.
This character's projectile can be used to either disrupt opponents or bait approaches, Yes disrupt = gimp, what Spring is best used for.. otherwise if used on the stage, it definitely baits approaches as I described above
and can even be used in approaches, even though it can be shielded. A common tactic with Sonic is to approach into a shorthop -> footstool -> Spring; but if they shield your approach (spindash or dash attack, or shieldgrab a run) then the Sonic loses, so his approach is tough, but can be effective if it's mixed up well.
However, due to certain characteristics and matchups, Obviously this is talking about his lack of KO power and predictability of some moves (homing attack, Dair), and his bad matchups particularly against metaknight and wario
this character may not reach the ranks of top tier, but certainly is not bottom tier material. Sonic will never be top tier but is definitely not bottom, like everyone on the Sonic forum knows.