Finally! I found a person who claims that Mango Lassi and Milk-shake taste different to him: Daf. So I see no choice but to change my claim to:
Mango-Lassi is the name of a typical 'western' drink that consists of two extremely delicious items: Lassi and Mango. However, the drink is completely unknown to people who are born and raised in a particular town in the south-eastern part of Sindh which is famous for it's production of Mangoes and a particular Lassi shop all around Pakistan. IMHO, those people should not be blamed for their ignorance since they are quite far from the western world to know about such new inventions.