Every ad platform you use is learning from a sample. The question is how biased that sample is.
Between ad blockers, iOS restrictions and consent banners, somewhere between 30 and 40% of browser-fired conversions never arrive. That is not evenly distributed — it skews toward exactly the privacy-conscious, higher-income users most advertisers say they want.
The fix is not complicated, it is just unglamorous: fire the conversion from your server, deduplicate it against the browser event with a shared id, and send the platform the click identifiers it needs to attribute it.