Correct, and that goes back to the risk a seller is taking when accepting those kinds of payment types. It's extremely easy to do a charge back on Paypal. So if someone is accepting a payment for BTC via paypal, where there isn't really a tangible good being exchanged, the buyer is almost always going to be out of luck if a charge back does occur.
Same thing with gift cards. Someone can buy a $1000 Egift card with a stolen credit card, buy $500 worth of BTC with it, then a few days/weeks/months later, when its found out that the gift card was purchased fraudulently, whatever balance is left on it becomes void.
Bitcoin exchanges are places you can almost openly flaunt fraud and get away with it. Here's an example of an ad where someone wants to buy your BTC with an airline gift card for $8,000 when it's only worth $4,000
"Get double the money for your coin. Once you receive gift codes and confirm balance, you are expected to release coins immediately. Travel must be made within 3 days after trade. I am not responsible for any loss after this time frame."
This is straight up telling you, "I bought this with a stolen card, you need to travel within 3 days before the airline realizes it and cancels the tickets you bought with this stolen gift card".
I'm all for getting the best deal you can, but even if I had a guarantee the cards wouldn't go bad, I'm not comfortable being part of something that almost certainly has some kind of fraud/theft attached to it. Others are fine due to out of sight out of mind, others are fine because they don't give a shit.
This is why the cash deposit is the safest option, because it's nearly impossible to do any kind of reversal after the fact with cash transactions.
They do have a review system, kind of like Ebay does. The important thing when looking at someone's rating is not to just look at their feedback percentage. Here are two examples:
Seller A:
Feedback 100%
Total BTC traded: 250-300
Total Transactions 3000+
Different Partners Traded with: 3000+
Account is 2 years old
Seller B:
Feedback 100%
Total BTC traded: 1-5
Total Transactions: 8
Different Partners Traded with: 1
Account is 1 week old
The first guy is likely an established trader who you shouldn't have many problems with. His account has been around for awhile, and he has a high trade volume with numerous people
The second guy just created an account, and has likely sent BTC back and forth between himself and a friend in order to start building a false track record and get that 100% feedback score