A YouTube Help thread has a notification from a top contributor of the forum that your YouTube earnings will no longer be reported within the Google AdSense reports after November 1st.

Colette W. wrote:

Peggy K. added a few more points:

on November 1st Hosted AdSense for Content / AdSense for Content Host earnings will drop to $0 in your AdSense account.
payments will continue to be made through AdSense. That means being sure all holds are removed from your AdSense account for payment
control of ad blocking will continue to be done from inside your AdSense account

Google launched AdSense video units back in 2007, it was known to be paid differently than typical AdSense ads. But it was confusing how the reports were on both YouTube and AdSense and didn’t always match up 100%.

So I guess this is the rational.

Forum discussion at YouTube Help.