It's illuminating to contrast Bix's opening chorus on "Dusky Stevedore" with "Bless You Sister" (its session-mate and coupling on OKeh 41100), which also starts with him soloing a full (bridge-less) chorus. Note that both songs were brand-new, and the boys probably were tackling them for the first time.
"Bless You" is a full-out re-imagining of the tune, a gorgeously improvised composition similar to the famous "Singin' the Blues" chorus. It's so beautiful, we don't care that Bix never comes near the original melody (hinted at by the saxes behind him). Relying totally on his imagination and skill, Bix is definitive, with no trace of a mis-step or uncertainty (and it's one of the least-mentioned of his celebrated solos).
"Dusky" - on the other hand - is a business-like, earnest attempt to lay down the original melody, for the sake of delivering the tune more or less intact, as Bix did at the beginning of "Ol' Man River." He's READING these notes.
This is why I'm certain that Bix's chorus on "Dusky Stevedore" has a lot more to do with "getting it right" than being creative. It seems obvious in this case that Bix used his creativity to dig himself out of the hole he'd dug by misreading the fourth and fifth bars of the tune.