Every single normally functioning human being has ABdominal muscles.
Many people seem to think that just because someones ab muscles are visible this implies superior strength to those without abs.
The human body changes all the time, his metabolism rate may be superior to yours thus having the ability to burn more fat quicker than yourself.
Ane xample of this being my brother who eats junk food constantly throughout the day, smokes, drinks everything yet hes skinnier than myself and older than myself even though i train.
Just watch the world strongman competitions.... not one of those guys has a visible sixpack.