I think what your cousin said is probably true to his industry. Certain industries are very competitive and getting your foot in the door is half the battle. Positions like that usually aren't advertised and you need to network and have connections to land a job. Obviously that isn't true for every industry, and some of what he said just doesn't make sense. Some places specifically state not to call them. And if anyone were to repeatedly call a hiring manager I would think that would get him/her taken out of the running for being annoying.
Sounds like you are having good luck in your job search and I'm sure you will find a job quickly.