My point was the fusible link is to protect the main circuit from the power stored in the battery if its given a direct path to ground. That load will be very high - whatever the wires can carry, certainly a 100 amps or more. That's what it takes for the fusible link to melt quickly.
If any of the wires in the main harness are grounded, the link will melt in seconds. Of course if any of the wires or connections between battery positive and grounding point are in poor condition - they may go first. :(