Alcohol tolerance is not static, there’s a variety of factors that affect tolerance as well as absorption rate. When I was drinking daily I was able to take 5 shots in a row just fine in the middle of the day without blacking out. Doesn’t mean I wouldn’t be blackout drunk if I took 5 shots now at the same weight given that I drink 1-2 beers once or twice a year, almost always the second one is because the first one got warm. It’s not uncommon for people to overestimate their tolerance to alcohol.