Technically he is correct to say the stall served the wrong type of prawns different from what they said in the menu.
But if he can see the stall operator is a Chinese guy. Maybe he meant China mainland male hawker.
Then it is foolish of the customer to expect this China man hawker to be honourable about medical fees claim.
One can also say the customer is stupid to eat at such "hot pot buffet".
The hawkers need to make money.
It is expected they will cut corners for higher profit.
Personally I do not consider tiger prawns as superior or better than normal prawns.
By the way, they LOOK different.
Thus I am astounded the customer cannot tell the difference.