You're correct in your statements from Brand. If you REALLY want to get into some good stuff, look up Stan Hugill.
As to the modern use?
I can attest that in today's modern US Navy, shanty singing is not only dead, but generally reviled. Along with the general decline of the average enlistee down towards the common denominator has come the bizarre hatred for folk music.
Even in otherwise traditional (and still observed) activities such as the Shellback Ceremony, no music is used.
This MAY be different in smaller ships, but amongst myself and my few friends with service experience, shantying in ANY form pretty much died out after the rash of 'destroyer shanties' in WWII.