My bet about how they are choosing the 1000 subs and 4000 hours watchtime criteria: it is about to get this number as tractable as possible, considering they will now manually review your channel prior to monetization. Even with their smart machine learning algorithm, they cannot scale beyond this number.

It is a little insincere to use the 99% of the channels number here. Vast majority of the channels from Youtube makes barely better than nothing because the long tail effect. What is actually interesting is, how many of the channels that previously make around a sizable chunk of money from Youtube, like say 1000 dollars, now will not qualify. I bet it won't be as harmless as Youtube want people to believe here, but they probably believe it is inevitable casualty.