Amp Breaker

My thinking on a factory system is that any short will shut down the alternator.
(a) current flows to ground so why would it go through the rotor? the rotor is not the easiest path.
No field = no power out.
(b) current flows to ground so why would it go the ignition? No ignition = no engine = rotor stops turning and no power out.

The fusible link or links is to stop the battery from discharging when an unfused circuit shorts. On our cars it really only protects the main feeds. Its a 16 gage wire so its not going to protect an ignition wire that's also 16 gage (or even 18 gage).