yes SameSite attribute controls the behaviour of the cookie SameSite=None allows the cookie to be sent to 3rd party (cross site), so google knows where it is coming from.
both hold cookies of google.com (with Samesite=none and secure flag)
please notice the cookie with name NID, both have same value on youtube.com and mail.google.com and both are Samesite=none with secure flag. And both of them issued by google.com (which is the master domain)
This behaviour is released by google chrome in 2020 in chrome version 80
The RFC for this feature came in 2016.
https://learn.microsoft.com/en-us/microsoftteams/platform/resources/samesite-cookie-update
https://web.dev/samesite-cookies-explained/
https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-cookie-same-site-00
https://stackoverflow.com/questions/60070572/setting-samesite-none-and-secure-in-asp-net
https://learn.microsoft.com/en-us/aspnet/samesite/system-web-samesite
https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.html#samesite-cookie-attribute
https://web.dev/samesite-cookies-explained/
https://learn.microsoft.com/en-us/microsoftteams/platform/resources/samesite-cookie-update
https://online-sales-marketing.com/googles-secure-cookie-policy-samesitenone/