It's more like this: A company contracts with a factory, they want 100,000 pair of shoes. The factory however is going to make a million or keep making it until there's no one to buy it. These are called "ghost shift" goods which is the bulk of counterfeits. If the product is not a limited run and still being produced the quality will be exactly the same. If the original manufacturer is no longer purchasing then the factory will very likely use cheaper materials.
The brands know this happens, they really don't care, what the brand will do is send a couple workers to the factory to be QC buyers. The factory makes a million items, and the QC workers will go through and pick out the best 100,000. The other 900,000 will be sold in the the developing world. The brand will typically take the 100,000 then send them to the US or Europe to another factory where they will have tags sewn in them and possibly some more labels or insignia attached. If it's a particularly premium brand they will add some secret identifying marks that even this LegitCheck website is unlikely to know about.
Those secret marks are typically for extremely high end goods that have lifetime warranties etc and the only time it's checked is if you send it in for warranty work.
A LOT of these goods are completely indistinguishable and will even make it into the retail supply chain. Particularly at stores like TJ Maxx, Bealls, and Ross et al. Though they go through a series of distributors that will basically only exist for a few shipments to avoid liability after some previous large lawsuits.
Ross and Burlington will also knowingly buy the ghost shift goods but keep them unbranded and sell them in stores with no labeling at all. You can find these clothes and they will have a tag sewn into that has a lot number. You can take that lot number and put it in to import manifest search engines and find out what brand was also importing them.
This would be where you find your coveted Fake / Knock off high quality with the best success.
