Wrong wrong wrongity wrong. This is not an issue of correlation and causation being confused, it’s well established scientific fact that drinking after blood donation changes your tolerance to alcohol. For one thing you have less blood to dilute the alcohol in your system, so BAC gets higher than it normally would from the same drink. The other problem is that blood donation increases the risk of dehydration, which can lead to passing out (or a massive hangover if you drink)

I am a frequent blood donor and my reading materials always say not to drink for 24 hours after a cycle. My FIL and his frat brothers used to donate blood and then drink (against advice) so they could get crazy wasted for cheap . It’s definitely not a great idea but people do it