We're trying to determine the impact of the removal of samesite=none cookies in Chrome; we've configured canary to test the third-party cookies phaseout, but we still see that Chrome both accepts samesite=none cookies and honors them on cross-site HTTP POSTs in the top-level browsing context.
yes our current plan is to only deprecate default access to cross-site cookies in subresource/nested contexts.
I would have expected cross-site POST operations (which are not idempotent) to no longer send any form of cookies with privacy sandbox?
This is not within the current scope for third-party cookie deprecation in Chrome. Such a change will likely be very disruptive to the ecosystem since it would impact common web payments and identity flows; so we will need to ensure compatibility.
from https://github.com/GoogleChromeLabs/privacy-sandbox-dev-support/discussions/143