It was last updated in 2017 per the date at the top, but yes, it's an older article.

This post indicates that 3p cookie issues only affect SSO providers without a hostname that lives within the primary websites domains: https://blogs.akamai.com/2020/01/cookies-single-sign-on-and-... (so SaaS offerings without domain masking). Is that your understanding?

Here's an interesting post on the samesite implications: https://www.troyhunt.com/promiscuous-cookies-and-their-impen...