Dress code confusion

Travel globally and dress locally. Wherever I go I copy the local dress. I was invited by my Muslim friend to stay with his family -parents and 3 brothers. First night everyone was gathered around the dining table. The men wear a short from naval to knees. The father of the house apologized that he did wear a shirt like me. I replied that I was honored that the family just acted as a normal family. When I enter a new environment I like to be a little bit overdressed. Two days later I adopted the shirtless dress code. My friend informed me straight away that I should wear a shirt. Now I know that a dress code is not equal for everyone. Although the family accepted me as part of their family I was not member of the core family of close relation between parents and children. Dress locally means also to analyze closely the information provided by your hosts.