I have not heard anyone seriously discuss that cooldown prevents compromise of the forge itself. It’s a concern but not the pressing concern today.

And no, however compromised packages to the forge happens, that is not the same thing as marking “urgent security hotfix” which would require manual approval from the forge maintainers, not an automated process. The only automated process would be a blackout period where automated scanners try to find issues and a cool off period where the release gets progressively to 100% of all projects that depend on it over the course of a few days or a week.