If we use Charlemagne or Genghis Kahn as our examples, then this doesn’t quite fit. They each had many wives (and non-wives) and many children from those wives, so the female UGA would be the common genealogical ancestor of those wives. But as you say, A&E are expected to be monogamous so this doesn’t apply in every case.
However, the MRCA for mitDNA and y-chrom are not expected to be a couple, so why wouldn’t the same apply to female and male MRUGA’s? I am not arguing against the idea, just that I don’t see any reason why this would be more likely.