1. Honey makes money through deals with retailers to not offer the best coupon code to the extension's users
2. Honey swaps out the referral code from the blog/video/etc. that actually referred you to the product with their own, even when they didn't find any coupon deal
Merely "Honey makes commissions from our merchant partners" is not at all a "very upfront" description of that behavior. Moreover, many of the people affected by this are reviewers/etc. who have never themselves used Honey so had no particular reason to look into how it works.