AdSense moving to pay per impression and updated revenue share
Next year AdSense is moving from primarily pay-per-click ads to pay-per-impression. They are also breaking down the revenue share for AdSense for Content to separate the amount taken by Google Ads or the third party advertising platform (about 15%) and AdSense (20%).
This does not affect YouTube ad revenue share (check that on your YouTube Studio Earn tab).
Google does not believe this will cause a significant change in revenue (hopefully correct!).