There's 3 hypotheses I have for why this is.
1. YouTube has been gradually rolling out the counter-blocking to an expanding number of randomly selected users.
2. YouTube doesn't bother blocking me because I've purchased a substantial amount of content from them. There's little benefit in discouraging me from buying more content in the future.
3. YouTube has done some analytics to figure out that I'm the kind of person who will never return if no ad blocking is allowed and doesn't trust them to keep ads out of Premium.
I don't suppose you've purchased shows or movies through YouTube?