I'm with you on that, and hope someone with domain knowledge can weigh in here and explain if there's a subtlety I've missed, but surely the presence of embryonic stem cells, haploid or not, means that there had to be a sperm, and hence a male mouse, to produce the embryo from which the stem cells were extracted? Even if, being haploid, those stem cells contain only the mothers' DNA, or other means have been used to 'edit out' any traces of male influence, that doesn't suggest the whole process could be done start to finish using only females. Or have I misunderstood something?