They're testing the waters to see what they can get away with. Last year they ran a trial where 4K playback was completely locked behind Premium for some users, which they walked back due to backlash, but they wanted to do it.

Likewise they want to break adblockers, and they are probably easily capable of doing so, but they're trying to triangulate exactly how much backlash they'll get before committing to it.

I don't think there is anything wrong with blocking ad blockers, backlash is just cause people feel entitled to consume content for free without paying their fair share to creators be it adsense or premium account share.