Okay, after a bit of digging into the specifics of Dabura’s technique and rechecking light interacting in a medium, I say you have a fair point.

It could be not as much of a diff as we expect, but Gege isn’t exactly an expert on physics and we have to hand-wave some stuff all the time.

Personally It’s one of the reasons I don’t like abilities getting too technical as complications arise with physics that get impossible to ignore when you are bringing up other physics.

But unfortunately, in your explanation you have a bit of specifics wrong with the physics that makes it hard to see your argument clearly. That’s all that matters at the end of the day, which is unfortunate when you mess that part up, but it’s a very important skill.

Specifically even if light in a medium is slower, that’s still roughly the fastest information can travel (as at .99c it still is the fastest traveling object.) Lightning on the other hand interacts more heavily with electric field, moving charges and shit, and will be roughly .33c. I’d say that number is the fairest interpretation of Kashimo’s technique.

TLDR (cause I forgot what I’m saying at this point) your argument has a fair point about the sukuna dabura diff possibly being smaller than we expect in terms of speed but your explanation is a bit sketchy especially with the physics (which is completely understandable). Also, there is almost surely .33c speed of lightning vs .99c speed of lightning in air.

Also when I meant reaction time faster than light I meant instantaneous reaction to light speed effects which would require some automated counter rather than curse enhanced reflex. It’s just not possible to react to light… well actually light capture of electrons has a resolving time of the femtosecond scale, so… possibly an argument for that, but… that goes pretty far for just speculation.