I was making the same assumption when looking for an explanation as to why my cockerels leave it late to start crowing. Digging a bit deeper, I've now come to the conclusion that our birds are normal and very young cockerels (chicks) aren't really crowing, whatever weird sounds come out of their beaks.
My reasoning is as follows. Chickens are birds, so what ornithology has to say about bird vocalisations is relevant. Ornithology usually distinguishes between calls, which are short, simple, usually single note/ sounds made by both sexes throughout the year (like alarm calls), and songs, which are long, complicated sounds produced normally by males only, with some seasonal and regional exceptions (Australasia, notably, and we've all read about crowing hens). So a crow is a sort of song. Song is said to have two principal functions, territorial defence, and mate attraction. Crowing starting up when the cockerel reaches sexual maturity obviously fits, being consistent with this. Our cockerels are behaving normally, no additional explanation required. Crowing in an immature cockerel is what requires explanation, assuming it is really crowing of course.
In a flock type situation, but even in a tribe situation, young males spend some time as sexually mature individuals before going their separate ways (or if the circumstances permit, stay with the flock).
We do know that males will usually start showing male-specific traits (albeit juvenile) before they start mating and/or crowing.
It seems logical to announce their gender to everyone way before they start acting upon their sexual urges. That way, they establish themselves as harmless, and not a threat/competition to any adult males.
When they do end up starting to mate, they are driven off (if at all) with much less force, because the head male(s) are used to their presence as males, not just “juveniles”.
The crow here seems to be the last step before sexual maturity; usually two weeks or so before they start mating.
That seems like the last step, a “I’m getting close to maturity” signal to the rest.
For the males, it’s when I’ve observed my adults start giving the cockerels more attention. They might be getting ready to make a decision, let them join the ranks, or kick them out.
For the hens, they start treating them more like males, and less like annoying juveniles. This is the age where I see pullets of the same age start forming preferences.
Still, incredibly immature crowing seems out of place. It would make sense as a very early “announcement”, but most cockerels that start very young don’t seem to realise what they’re doing.
My only experiences with early crowing were with Lady Gaga and his sons, but all of those were just incredibly fast to mature, not just crow