https://tools.ietf.org/html/draft-west-cookie-incrementalism spells out the proposal in a bit more detail.
As for who the audience is, perhaps people who were alarmed by the WSJ's scaremongering: https://www.wsj.com/articles/googles-new-privacy-tools-to-ma...
Someone leaked the news to the WSJ, which tried to spin this as an anti-competitive move.
<https://web.dev/samesite-cookies-explained/>
which does go into a good deal of technical detail. A challenge is that even experienced web developers didn't know much about SameSite prior to this announcement.
To that end, we've implemented the change behind two flags (chrome://flags/#same-site-by-default-cookies and chrome://flags/#cookies-without-same-site-must-be-secure) so that we can work with developers to help them migrate cookies that need to be accessible cross-site to `SameSite=None; Secure`.
Ideally, we won't unintentionally break anything when we're confident enough to ship this change.
I would even go so far to substitute "should" with "must". But it is a first step.