I don't think anyone with any sense is taking the song/poem as having any basis in reality.

I hope not. But better to prove it. :-) (And someone could, theoretically, have told a tall tale about a real ship.)

The only question seems to be how old it is and how much came from the pen of someone c1970. The only people with any interest in this are us obsessive pedants;-)

Yes, well, obsessive pedantry is why they (don't) pay me the big bucks. :-)