[Solumina]

With the translation it is hard to be sure but I got the impression that the kid knows what sex it is (as they said the kid know the difference between males and females) and they did make it clear that there was no intention to force the child to keep this a secret and that this will not continue forever. The whole thing is based on the idea that the child will learn the difference between the two sexes but with no attention paid (by the parents) to gender, after all gender and sex are not the same thing. Plenty of kids have been raised in a gender neutral environment, this just takes things a very small step further by actually continuing the gender neutrality outside of the home by not telling others the sex of the child.