It is an inconsistency that the Unknown father doesn't have the skeleton biography section. That is easily added since it is only three lines. An annoyance, for sure. A clean profile, as Ros says, is usually a better way to go since you then get what you want and can usually add the estimates of birth or death based on age of the siblings which should really be added.
I haven't found it rare that there isn't a hint for parents. Most of my ancestors who came to Canada have no hint whatsoever as to parentage. My wife has found the same thing.