But cross origin form posts are and have always been permitted, and are the main route by which CSRF vulnerabilities arise. Nothing on the client or server needs to be enabled to allow these form posts.
Furthermore, the approach detailed in the article simply has the server block requests if they are cross site/origin requests, so I'm not sure what the semantic difference is.
I feel like people are just parroting the OWASP "they're just defense in depth!" line without understanding what the actual underlying vulnerabilities are, namely:
1. If you're performing a sensitive operation on a GET, you're in trouble. But I think that is a bigger problem and you shouldn't do that.
2. If a user is on a particularly old browser, but these days SameSite support has been out on all major browsers for nearly a decade so I think that point is moot.
The problem I have with the "it's just defense in depth" line is people don't really understand how it protects against any underlying vulnerabilities. In that case, CSRF tokens add complexity without actually making you any safer.
I'd be happy to learn why my thinking is incorrect, i.e. where there's a vulnerability lurking that I'm not thinking of if you use SameSite Lax and only perform state changes on mutable methods.