This is all very true an I bet why TTT didn't 'out' them is because they paid them gazzilions for those 5 years, or it could be a part of their contract (disparaging clause).
But, the more interesting part is why honey doesn't show the 'best' coupons. It's very true, the owners of stores can control that aspect but their reason would be something like. Honey is an affiliate channel, so some coupons that are targeted for email campaigns, new customer acquisitions, or old customer win-back, would not qualify, as they are usually juicier, and would 'mess' with owners being able to gauge how well their other marketing campaigns are actually working. That's their basic reasoning anyway...
Reality is simple though - honey and other like them browsers are simply designed for lazy consumers, who will take any, not the best discount available. And, if they are this lazy, they are likely either being scammed like the video said, or oblivious to the last click.