I think, at this point, there isn't any article, blog, etc that sheds any further light on this matter for me. We are in a holding pattern until The Four actually follow through on their promised "formal correction". I'm not convinced that it will actually happen, so I will believe it when I see it.
Specifically this:
As the same website has now also revealed, in a separate article – although Professor Spaemann appears not yet to know of this speculation – the other two prelates who had earlier also signed the dubia which were sent to Pope Francis are “in all probability” the retired Curial Cardinal Paul Josef Cordes of Germany and His Beatitude Sviatoslav Shevchuk, Major Archbishop of the Ukrainian Greek Catholic Church.
The two other mystery signers of the dubia. I thought the involvement of an Eastern Rite bishop was particularly interesting, and might have something to do with the fact that Ecumenical Patriarch, Bartholomew I has suddenly, out of nowhere, found the need to become involved in this mess.
Eastern Rite involvement is a bit of a "wild card" and one on which Francis may not have counted.