Fingerprinting an Operating System helps a cracker because:

OS fingerprinting identifies the operating system type and version from network responses, not the specific application software installed on the host.

There is no such concept as a 'security-delayed window based on the port being scanned' - this is a fabricated distractor with no basis in networking or security.

OS fingerprinting does not bypass patches - a fully patched OS of the same version would still be identified but would not be vulnerable to the patched exploits.

Once an attacker knows the exact OS name and version from fingerprinting, they can cross-reference it against CVE databases and exploit repositories to identify unpatched vulnerabilities specific to that build. This targeted knowledge dramatically increases the efficiency and success rate of subsequent exploitation attempts.