You can't compare Yoogis to Tradesy, both have very different business models.
With Yoogis, they don't list the bag just based on your pictures. They require that you send the bag in so they can authenticate and then they take it upon themselves to photograph and list the item. They for sure know what item they're getting and if it is authentic or not. Keep in mind, for many of the superfake bags out there, many professional authenticators won't even authenticate without physically touching the bag. So Yoogis does all this to insure that everything is up to their standards. When you purchase with Yoogis, you're entering into a transaction with this particular business.
With Tradesy, you are entering into a contact/transaction with a private seller, not with the company itself. The company only offers a platform for sellers to sell. Which is why the commission fee is 9% vs. the 30% that Yoogis charges. They can't insure that all the bags on their site is 100% authentic. What if it is a super fake and it photographs like the real thing but when you receive it, it feels like plastic? I have seen Tradesy remove obvious fakes. But sometimes to hard to remove something that looks borderline "off", maybe because the seller is a bad photographer and took bad shots. Even on tpf, there have been instances where members thought a bag looked "off" and reported it as a fake, only to find out from senior authenticators that the bag was actually authentic. So there are lot of factors that go into why Tradesy won't take it upon itself to remove fakes that people are reporting (unless it's a super hideous fake). Whose to say the ones reporting aren't just reporting to take out their competition?
As a buyer, it is best to take it upon yourself to protect yourself and know what you're buying. There are definitely some great deals on Tradesy but that requires that you do a bit of homework. If you have no time for that or just don't care to put in the effort, then maybe it's best to buy on Yoogis or Fashiophile or even the boutique. The downside is you have to pay their inflated price. There's a cost to everything.