The main issue, it seems to me, isn't whether Hugill cribbed from or misconstrued the words of Terry, but whether he learned a version independently at sea.
What he "learned" from Spike Sennit was presumably the unbowdlerized form of the chantey, which itself would have explicated the obscured theme of Terry's printable version.
To dismiss this idea would be to assert, without evidence, that "Spike Sennit" was imaginary and that Hugill himself composed most of the lyrics he printed, based on what he found in Terry.
While Hugill could easily have elaborated the song on his own, the invention of a *named* fake source would hardly have been worth the trouble. Since Hugill's publishers forced him to "camouflage" throughout his collection, why on earth would he have cooked up a new version of a song he'd simply learned from someone else's book - a version he'd have to describe as "camouflaged" and inauthentic?
Whether any version was widely known, of course, is an unanswerable question.