If you start trading then start in bitcoin it will not let you face loss, but you will get profit from here especially use DCA it will help to reduce risk all the time. We know it's always better to use DCA as a smart investment.
It's an unhealthy advise telling someone to stick with Bitcoin when trading, deciding to trade with Bitcoin or any other cryptocurrencies issues same losses, nothing distinguishes the risk management, it all goes down to how the funds is being managed, using Bitcoin to trade does not stop you from losing as well. Anyone who is scared to lose should be focused on investing their funds in Bitcoin, either strategies are okay depending on the individual balance and how he understands the market.
I think this guy meant that Bitcoin has advantages in terms of trading over other cryptocurrencies.
But, I understand your point, in general, trading is really very dangerous, and even if you speculate with Bitcoin in an attempt to guess the price, you can lose your deposit as quickly as on roulette in gambling. And the fact that Bitcoin returned to ATH will not help here. Also, trading and speculating with the first cryptocurrency can make attempts to accumulate Bitcoin fickle, but investing according to DCA has advantages in this.
This method makes the one who wants to accumulate Bitcoin disciplined, despite all the other multiple advantages of this method.