Isn't it just like him! It would have been kind of interesting if POB had illustrated the nameless to Jack bit by, for example, saying "Private, hail that boat!" but then, it does show that they weren't nameless to Jack by having him address the man by name... and there are plenty of other times when a Marine is 'just' a Marine, with no name given.

And I do like how Jack inspects the Marines first and then gives them permission to change into their duck jackets (drill jackets - the white off-duty jackets shown in the film).