It's not a dubious claim, just his personal experience.
I switched to uBlock for a few years ago and had the opposite problem, it just seemed to break a few websites.
I didn't really dig into it, but from memory it seemed to be blocking a lot of requests it shouldn't resulting in things like Facebook Messenger breaking. So it's interesting that you point out they both use EasyList.
Perhaps I'll give it another try, but honestly, i don't notice any adverts with ABP so i tend to forget it's even there. I definitely noticed when uBO was installed.