^^ I've seen quite a few albums with hair like yours (mook) where ppl claim 4a. The coils in Noni's pics are very uniform - I thought the definition of 4b hair is that the coils are not uniform. Not to mention of course some have different types of hair in different parts of their head and some have different types of strands growing in the same areas of the head. So I agree it's confusing. The 4 category system is incomplete and a guideline not the final word on anything. There was a link to the naani website where "ms naani" or someone else has added an additional category and now there are 5 types.
Coils that are flexible rarely stay 100% uniform throughout their length, especially if they have a very small diameter. But the general shape is a coil/curl even if some parts don't form perfect shapes. I don't think there's a single person with curly hair who doesn't have that direction change somewhere in his/her tresses.
Examples:
This is clearly 4A hair, known to get well defined clumped coils with a WNG:
But a close look at the coils shows that they aren't all perfect coils:
And here's a type 3 head. No question about whether this hair has coils/curls, right?
A close look at this type 3 hair shows you that coils don't really have a set rule on how they look, but there's no mistaking the general shape:
Likewise, type 4B coils can also seem to change direction here and there but they are still coils nonetheless. Even in the pics I posted of my coils, there are some that form weird bends like the hair you see above. See right next to my nail in the pic to the left:
Such is the manner in which flexible curls/coils behave.
Lack of uniformity isn't only in 4B. It's in all curly hair.
Even Miss Curly Locks herself, Shirley Temple, was not exempt from coils doing their own thang, but coz they're compact, they seem perfect. But Im sure if you stretched them out, you'd see this common trait of non-uniformity
And here's one more curly head with all sorts of strange things going on and hardly any uniformity, but no one would deny that she has curly hair: