OK I think I got it.
The first couple of paragraphs says the the most wear with wire rope in crane service is rolling over the pulleys caused damage to wire.
Usually, fatigue breaks develop in segments of the rope surface that come into direct contact with a sheave or drum.
If that is the case then bad strands will show up before any other damage is critical in a crane.
With a boat since the wire don't move it can fail first in places that can not be seen.