Has it been a long time since a mechanic has looked under your hood? These battery condition/cable maintiance issues isually get caught at normal service interval times.
If your car had exibited a "no crank" condition due to a battery or cable problem "tapping on the alternator would not fix it. If fact tapping on the alternator will not fix anything.
We do get many posts relating what a AAA person does or says, and many times their diagnosis is suspect. I conclude people think "since my car started after AAA got here they must have done something right".