This isnt a really good reason to not run windows, they have similar 0days for any nix system as well.
I have watched very closely for 20 years now for any chatter or evidence of a FreeBSD/OpenBSD zero-day vuln that was weaponized or sold or used for state-sponsored covert action and I am not aware of any.
None of the leaked information from Snowden, et. al, gave any evidence of their existence either.
Technically speaking they should exist but I'm not seeing them ...
Further, if you were worried about attackers or hardening a system, etc., you wouldn't be running samba (or anything like it).
I'm talking about a remote-root vuln in the FreeBSD kernel or in any of the default system daemons that were bundled with an OS release (like openssh, crond, syslogd, etc.)