It's said that using Chidori impairs the user's vision because of how fast the user moves, but where's the sense in this? Using Chidori doesn't make you faster, it's just you running towards an enemy at top speed and stabbing them. By this same logic, using Rasengan or literally anything that includes you charging in should also give tunnel vision. Even if a user uses more speed to perform Chidori than any other jutsu, they could still dial back their speed and perform Chidori. E.g. Adult Kakashi is probably vastly faster than Kid Kakashi, so performing a Chidori at Kid Kakashi's speed SHOULDN'T give him tunnel vision because he's adjusted to that speed.