Gibb would be able to put more meat on the bones, but the Stevedores in the Gulf ports were already singing proper chanties i.e., songs with a chorus that were taken into the chanty repertoire) for screwing the cotton, before they came aboard ship if I recall correctly from Gibb's writing.

All of this is well and good and equivalents in other periods are still very interesting but establishing a direct link from any of these to the chanties we know seems to be all supposition.