I don't see how it's possible that "look at every single byte for the unescaped balanced quote/bracket that ends the field/record" could be faster than "read th

I don't see how it's possible that "look at every single byte for the unescaped balanced quote/bracket that ends the field/record" could be faster than "read the length, read the whole field in optimal buffer sizes". I suppose there's other stuff that's being done that could be suboptimal, but that's the key difference.