This is absolutely not true. Anecdotally speaking: My fiancé who has helped me sell on Amazon for the past 4 years still gets confused when she goes to a listing and there is no direct offering or price listed. I've watched my grandma shop on Amazon and if there isn't an "add to cart" she moves on. These are both people who go to Amazon first to buy stupid stuff.
My profession is in software engineering and I guarantee Amazon has strong metrics around the efficacy of the buy box. Amazon has numerous "automated" policies in place to dissuade sellers from selling stuff for a "high price", forcing the use of undercutting to take the buy box, and enforcing quality metrics. They do anything they can to make it difficult as a seller to get top $ for your items because it's disadvantageous to Amazon's image as well as throughput.
Many of these policies are relatively new. Less than 3 years ago the buy box rotated amongst sellers in a nearly uniform manner. Now its based on seller volume, first to the price, quantity in stock, quality of stock and location. The introduction of the gouging mechanic has functionally killed hundreds of viable lego listings that weren't truly gouged. Removal of buy box is another and is part of the anti gouging mechanic.
The only mechanic that is advantageous for sellers that was recently more broadly implemented is the discount mechanic which has been a great help.