According to the newsletter, Cardinal Arinze's response, received in June, said that the relevant norms were intended "to ensure within broad limits a certain uniformity of posture" but at the same time "to not regulate posture rigidly in such a way that those who wish to kneel or sit would no longer be free." IOW, the faithful can do whatever they want.
Sure glad we've got these rubricians who are on top of things!