he should only swap the coins and keep. Besides, after selling coins into fiat currency, there might be an emergency, and you won't know when you will use the money to solve it.
I think it's also easier and convenient rather than taking it out of the platform. At least that way you can easily swap it when you want to or when you feel that the price is best to buy now.
There's also a higher chance to save the money if you don't directly hold it.