You already know me, just not under this username! I try not to put my name directly out on forums like this, but I run https://approximated.app and those 100k+ domains aren't all in one cluster, though some clusters are growing quickly and might be there in a few months. Customers paying for the clusters are generally SAAS or hosting related so they can bring a lot of user domains when they come on board and tend to grow steadily.
I keep telling people "tens of thousands" when I probably should be saying "hundreds of thousands"...