The anticipation is killing me
I shouldn't have said react as that isn't what I meant, still half asleep lol. What I did mean is that if used too much an opponent can read/anticipate the next one and jump in, as you perfectly summed up with ranges and the dead zone.You're not reacting to a 14frame projectile, plain and simple. Know your ranges, which are 1. around poke range and 2. outside of the opponents jump arc.
Projectiles thrown in zone 1 are unreactable, only way you're getting hit here is on a read, projectiles in zone 2 are reactable but are safe from jump ins, most armor but can lose to teleports. The area between these two spaces are a fireball dead zone where your opponent can react and punish or begin their pressure because you don't have time to counter their attempt to get in.
As for low sai I use primarly to counter projectiles from full screen and to help keep opponents honest in neutral, with my ultimate goal being I want them to jump so I can AA with roll or punish armor attempts in.