I think the terminology used in the book was intended as a rhetorical statement to invite curiosity and serves the books narrative to enforce the argument that many ships captains, in the age of steam, were woefully unprepared for the rapid passage through waters compared to their earlier sail and paddle-powered experience.
This is supported by statements made during the British Inquiry;
"The difficulty one has and which has confronted the Court from the first, is how is it
they failed to detect it until it was so close upon them?"
(Sir Rufus Isaacs, Attorney-General, British Wreck Commissioners Inquiry, Day 36. Final Arguments)
Lightoller stated, that he was confident that he would see "any ice that was large enough to damage the ship." He then went on to say in reply;
"I judged that I could see a growler at a mile and a half, more probably two miles."
(Brit Inq 13567)
"How far would you see one of these dark bergs on a clear night, assuming it to be 60 to 80 feet high? Shackleton replied – "It might be only three miles, depending on the night and depending almost entirely on the condition of the sea at the time.
(Brit Inq 25040-42)
In my opinion, the book draws on the evidence given by these statements and others, and elaborates on many factors that may have answered, to a large extent, the question posed by the Attorney-General at the time; i.e. " . . .
how is it they failed to detect it until it was so close upon them?"
Furthermore, the book is not based on that one statement, far from it.