That is, indeed, my predominant view, RiccardoLS: that the original probably consisted of 22, and that a number of cards are missing (including some obvious minors).
The question which arises for me is whether a number of majors slowly made their way into what is Tarot. I have no questions about the number of Majors which needs to be included for a deck to be Tarot (ie, 22) - do we need to assume, however, that those two cards were part of the original ones painted. I do think it is normal to consider that they were originally there, and for (good) reasons, were 'lost'.
When, however, we consider seriously the possibility that the deck just didn't have them at all, a coherent whole also results. I am not saying that the cards painted for the Viconti-Sforza family did not include these cards. Rather, that this may well be the case.
Looking occasionally at that deck, I even have the impression that the deck may have consisted of an even smaller number of original majors... added to only later.
I suppose that, from my perspective, and as I don't consider the Visconti-Sforza reflecting the Tarot's arch-type (in its platonic, not jungian, sense), I don't mind seriously considering that it leaves certain key and important features 'out', either for artistic, political, local, social or religious considerations.