The Sheffield and the Belgrano were not sunk using small arms... that is what I think the author is referring to.
Considering that the Frigate was standing by, and the two assault boats had heavy machine guns mounted plus a number of commandos, the skinnies were obviously at a loss.
So poorly written it's hard to tell.
Google the “Altmark Incident” February 16 1940, not only did the Royal Navy board an enemy ship, they fought the Germans with cutlasses. This last detail tickled Churchill pink, he loved the idea that even in 1940 British sailors could still fight their way on to the deck of a ship swinging cutlasses. Buckling the old swash and all that, eh what?