I wonder if they actually watch the ads on purpose, even in private or if they turn their adblocker off just for the video, as not to give ideas to their viewers and potentially losing ad revenue.
The chance that he was using one the whole damn time? 100%
Instead of adblockers, I remember sites that are user hostile one way or another and just avoid those sites. Those sites that are heavy on ads usually aren't worth my time anyway, so the presence of those auto-playing videos in every corner ends up being a signal for me to go somewhere else.