[oasisbob]

Both of those examples strike me as very contrived.

I can't think of anyone who cares that much about timekeeping who isn't running their own internal NTP infrastructure.

Google's Spanner requires accurate global time, so they deployed GPS and atomic clocks. Same for CDMA. There are some applications for high-resolution time (eg finance), so protocols like PTP exist.

A smeared NTP source in an otherwise normal list of time sources doesn't seem like that big of a deal either - eventually the daemon is just going to mark it as a falseticker and life goes on.