That's the definition of 4a...4a is smaller than pencil size to coffee stirrer size and smaller. The definition of 4B is hair that is fluffy with no curl pattern, even when stretched. All the number/letters have range so if you see ppl with bigger curls/coils, you might be the same hair type or they may have mistyped themselves. Have you seen the pen spring thread? Lots of 4as have pen springs. Picture thread attempt 4a, pen spring ladies
The number/letters are only about curl circumference. Ppl who say they are 4C+ tend to cite their reasons being that they have no curl/coil whatsoever or their hair is "very nappy." How fine or coarse the hair is, is irrelevant. If there's no curl/coil pattern, its 4B.