Thoughts on sample/early release pairs?

Generally curious about this. Been seeing more and more "plugs" on instagram with sample pairs. How legit do you guys think these people are? Like how is it possible that they have sample pairs in multiple sizes? Recently stumbled upon a thread on reddit with someone calling out one of the sellers and he would not show certain pics of the shoes. The poster was also showing conversations he had with the Chinese seller who sells the shoes to one of the instagram sellers.