This is actually a nice feature, why would I need to opt in to it?
For AI, I expect noise-signal will be not as good as I expect.
It's a non starter to have that critical context stripped out and be given an opaque answer by an AI without having seen the underlying information in the context it originated from.
It's not like it generating new information. It just summarizes information based on the same links you would have gotten without it.
Main metrics for their business is engagements(how many queries you do on google.com) and Ads clicks, and not how precise answer you got.