I ’oogled your question. Among the hits resulting, this looked relevant:
https://www.frugalforless.com/10-amazon-review-sites-that-will-get-you-free-amazon-products/
Looks like Vipon started off as an Amazon review mill. Perhaps it still is, basically they’re basing their reputation on yours for honest reviews.
I’d think both Amazon’s and the FTC’s rules would apply, since Vipon is just doing a man-in-the-middle job between you and Amazon’s sellers.