I spent years manually reconciling GA4 and Meta Ads data just to avoid those...

https://titussnewblog.lowescouponn.com/the-art-of-independent-data-verification-why-your-agency-reports-are-probably-wrong

I spent years manually reconciling GA4 and Meta Ads data just to avoid those panicked client correction emails. We used to burn 45 minutes of QA per client every single month