He did go to the Final World, though? That's where he meets Yozora in Remind. After that, it's really unclear what's happening. We don't really know what's going on. In the "Yozora" secret ending we see Sora wandering Quadratum and Riku who is also wandering Quadratum. Crucially, they don't ever meet. This could be a situation like in DDD where they are in different versions of the same place. it's also possible none of Sora, Riku, Yozora, or the Master of Masters are in the same version of Quadratum. None of them are ever seen in the same uncut shot which would definitively prove that they were. Although not uncut, the way it is cut seems to suggest the Yozora and Riku are in the same place, at least.
In Remind, the Quadratum that Sora and Yozora fight in is, if my theory is correct, not actually real Quadratum (My theory is that Yozora used the power of waking on Sora and they fought in a dream version of the Verum Rex videogame version of Quadratum). But regardless, If Sora wins the fight, he's seen in the final world. If Sora loses he is crystalized in (possibly) Quadratum. Yozora wakes up in a car which is presumably driving through Quadratum. If it is Quadratum, then where they were fighting can't have been Quadratum.
So, who knows. Maybe Sora is actually in Quadratum, maybe he's not.