It's counted as a view, and beyond that, in general the content creator gets a higher payout from Premium viewers than from ad viewing users.

I'd worry that if this is really caused by an adblocker, it's possible YT uses these same view counting mechanism that's being blocked to increment their Premium views, meaning Premium subscribers who don't explicitly turn their blocker off on YouTube could be being undercounted. If so that should be fixed, for Premium viewership, as that's not really fair to anyone.