This is true - if you are confident you will be here for 20 years then you would be mad not to take the allowance and buy somewhere - at the end of those two decades you have a free house.
But, buyer beware, during Covid, a lot of people found out that they weren't going to be here for 20 years after all. Many had to sell quickly, some had negative equity. Are you sure you will be in Dubai long enough to pay off most of the mortgage? Are you sure you will be able to keep your medical that long? Maybe nothing will go wrong and you (or your family) will just decide they have had enough of Dubai but you won't be able to leave because you can't sell your property.
Certainly buying a property in Dubai can work out very well, and does for many people, but go into it with your eyes wide open and know what you are getting into. It is probably nothing like buying a house in your home country.