This means, if I sell you one phone, and you pay me in bitcoin, but my phone is broken and you only realize that after you got it, you have no protection, and that's a big trouble. If you bought it with fiat, you would have the courts on your side and you would definitely try to get your money back.
What about the other way around? If someone buys a phone from you using fiat, go away with the phone while the phone is in good condition, but later on, you realize that the guy opened a dispute or chargeback against your account from his bank and your funds are now confiscated by your bank and your account is frozen because of the report. The bank will ask you for proof for the payment, and if you don't have a shop, and it was only a private and one-time deal you did with someone random, you are screwed because that guy who opened the dispute will definitely not help you get it removed.
In such cases, Bitcoin and other cryptocurrencies are very useful and beneficial because once a person makes a payment to you and it gets confirmed, they can't do anything about it because you can't do chargebacks or disputes in cryptocurrencies since it goes into the blockchain and can't get taken back.
