There's a big difference between "proper" and "more accurate than 99.999999999% of people care about" though. How many microseconds of accuracy do most people need? How many does openntpd provide and how many does the other ntpd provide? Claiming it isn't "proper" because in theory it may be 2 microseconds less accurate in some circumstances sounds like FUD.
Reach a reasonable accuracy. We are not after the last microseconds.
Whereas NTP looks for maximum accuracy.