I don't think "sub" means that it's still close. Being below doesn't have to be just a little bit below it. Why does being below have to be just a little bit below? This is where I get confused.
Because that's what it means? Like idk what to tell you, that's what the term means, it's used for speed close to but below light, used in contexts talking about relativistic velocity approaching light.
Sub is being used to denote it's below, but the term is used for speeds approaching. It literally just means "close to, but not quite". This is how that word is used in Japanese, this is ALSO the intent the word is being used in.
Again, subtropics, you wouldn't call the artic subtropical would you? Of course not, because subtropics, despite using 亜 too, still has an established usage. Thinking about it as "sub" as used in english is wrong anyway, it
isn't english to begin with, we just use the equilavent words or words that convey the meaning to convey what the japanese text means, which is
why it's often translated as "near" instead, because it conveys what it means better to english speakers, which case and point, you're proving exactly that, you're getting confused because sub doesn't inherently mean what the word is being used for in the line.
Vaporizing rocks is already a proud achievement for speed, but does it need to be near-lightspeed to vaporize a rock a few centimeters in size? I don't think it needs to be Relativistic+ fast to do that. A meteorite only needs to go as fast as
2000-4000 m/s to vaporize, which is pretty fast for most people.
Literally missing the point. It's stating because he can nullify all that, he can toss rocks at speeds just below light. He would not be able to because they'd long since evaporate if tossed without that ability. That doesn't change the fact it's emphasizing the cap of what he can do without such restrictions.