I read the Vatican not as expressing any type of doubt but of not having an opinion, "regardless of whether it's valid, it's illicit" or "it doesn't really matter because they're not authorized". Now, the Vatican probably would not doubt a Lutheran "ordination", or that of a Baptist preacher, so their opinion one way or another is worthless.
If you reread the announcement, the Vatican firstly discusses liceity, then passing to validity, states, “whatever about the validity,” and proceeds to announce it does not recognize the “ordinations.”
In other words, Rome is not still discussing liceity, or limiting/directing its non-recognition to not recognizing their jurisdiction, but to not recognizing the ordination (consecration) itself.
It is as though with the dismissive phrase “whatever about the validity,” Rome considers the matter too complex and murky to render a certain opinion/judgment, and therefore simply proceeds to announce it will not recognize them as bishops.
But if that is a correct reading of Rome’s announcement, it is the same thing as saying “we consider the matter doubtful, or capable of question.”