the comments in this thread basically back it up, but I'd frame it differently.
it's not just "authenticity works." It's that when you've actually used the thing, your copy gets specific. you nail the use cases, you know which problem it really kills, and you can talk about the tradeoffs without sounding like you copied and pasted the vendor's landing page. Seen that garbage from affiliates for years - including myself.
That shift matters because the reader stops asking "does it have good features" and starts asking "is this actually for me?" When the recommendation lines up with their real situation, they hesitate less before hitting buy.
There's also a selection effect at play. Cut 60% of the offers and you've likely ditched the weak products with shite funnels and a bad audience fit from the start. so that doubled conversion rate? probably a cocktail of trust, specificity, and better product fit.
the real lesson is dead simple: don't pick by commission rate and then force yourself to believe. start with the buyer's problem. find products you can honestly explain and defend. promote the ones that actually fit. Everything else is noise