AFAIK FreeBSD project tries to ship basic tools in pretty much every area (eg. DNS resolver etc.) that works for 99% of users and if anyone needs something more advanced, they are welcome to use ports.
That it exactly why BIND was replaced with Unbound and LDNS tools. Why not go the same way with ntpd? Openntpd is just the same to ntpd as Unbound is to BIND - a simple tool that works for most users.
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