Acausal sexual reproduction is quite plausible, in a sense. Suppose you were a single woman living in a society with access to sophisticated genetic engineering, and you wanted to give birth to a child that was biologically yours and not do any unnatural optimizing. You could envision your ideal mate in detail, reverse-engineer the genetics of this man, and then create a sperm population that the man could have produced had he existed. I can easily imagine a genetic engineer offering this service: you walk into the office, describe the man's physical attributes, personality, and even life history, and the engineer does the rest as much as is possible (in this society, we know that a plurality of men who played shortstop in Little League have a certain allele, etc.) The child could grow up and meaningfully learn things about the counterfactual father--if you learned that the father was prone to depression, that would mean that you should watch out for that as well.

If the mother really wants to, she can take things further and specify that the man should be the kind of person who would have, had he existed, gone through the analogous procedure (with a surrogate or artificial womb), and that the counterfactual woman he would have specified would have been her. In this case, we can say that the man and the woman have acausally reproduced.