That simply won't do for OP as he seems to want solely client only mode implementation of NTP. chrony supports both. He seems to think the authors of these daemons don't have his best interests at heart by adding functionality he doesn't want personally yet many other people will use.
I fully agree with him that client-only mode deserves its own program, given that less than 1% of all computers ever need to be NTP servers.
And yet he wants to go systemd...
OSX uses sntp which is open source, but it sucks because it doesn't stay running so it doesn't establish a PLL feedback loop that ntimed and ntp do.
Q: Does openntpd hook into PLL infrastructure?
How is that different than running the existing code in client only mode? That configured operation is just as easy to test and verify.