You’re confusing “feedback” with product “reviews”. Feedback is where Buyers leave feedback on the Seller for the Seller’s performance. Reviews are left for a product that describe its performance and if it matches the description.
Both are great and can influence a sale, but in the overall scheme of sales on Amazon, for the most part neither matter (unless the feedback and reviews are bad). People buy on Amazon because it is ‘Amazon’. Most don’t even really think about where the product is coming from, usually third-party sellers, but think everything they buy on Amazon is coming from Amazon.
If your client’s product has what they want, appeals to them and they like the price, they’ll buy it, after all they have the Amazon 30 day money back guarantee, no questions asked.
Your biggest responsibility to your client is to make sure you follow ALL of Amazon’s rules exactly and don’t break any of them. Many sellers do get away with breaking little rules here and there, but if caught it can bring down their whole business on Amazon, quickly and PERMANENTLY.
Read all the rules AND follow the forums. Arguing with the rules won’t change them.