if I were you and had 0.2 BTC funds, of course I would not buy just one coin, of course I would buy several top 10 coins based on Coinmarketcap, if you have that much funds and only choose one coin it will be very heavy and big the risk you will take.
Everyone has their own way and reason for carrying out their plans for investing and trading, because when the market is not bullrun, then choosing a good coin is also not a wrong decision, although the advice you give is also very good to implement and run for the long term