The answer is that the Unknown Head stands as a single governmental order which requires it to be this way with these uncertainties. And because of its power and control, these uncertainties are also found in the other Partzufim as aspects that develop as a result. The uncertainties we are talking about are not the normal kind of uncertainties where we are in doubt about whether something is or is not the case.
With regard to the uncertainties discussed in relation to the Unknown Head, the truth is that all the different combinations of MaH and BaN do indeed exist (even though they appear contradictory). Bearing this in mind will help you to understand why it is that the uncertainties we are discussing arise, especially all the details discussed by the ARI of blessed memory, which we could not have conceived at all.
Granted, there may be matters of doubt relating to the lights and vessels of BaN and all that depends on this. But as for all the other uncertainties relating to the detailed interconnections between MaH and BaN in the Unknown Head (Etz Chayim, Shaar Atik ch. 3) – what is the reason for the uncertainty?