It is true. Partner sites make revenue for the partner through revshare and partners attempt to create fake clicks and even conversions to inflate their revenue. Cobra effect in play.

This risk is zero (except for things like ad neuseam) on first party / owned and operated placements like search/ig/fb.

As with anything you should verify your roi through third party measurement providers, just like you would do for others.

Disclaimer: current fb ads engineer, former google ads engineer.