SzplitzOnSzplug:
Or were the English books published completely out of order?
Yep, that's the reason. In order to break Tintin into the rather difficult, comics-hostile UK children's book market of the late 1950s, the UK publishers Methuen started with what they saw as the most appealing stories to a readership who were new to Tintin. (Interestingly, Speilberg and Jackson seem to be choosing a similar staring point in the series to introduce Tintin to cinema-goers.)
And as they brought the books out in their new "incorrect" sequence, the English translators added a few continuity text tweaks to make their publishing order seem more logical as an actual chronological order. There are several others, as well as this Castafiore one you've noticed. These tweaks do tend to raise as many problems of chronological illogicality as they solve, and it's arguable that all these tweaks and fudges could now be usefully removed from the English translations, now that we have all the books in English and can read them in the original correct order.
That said, Hergé himself didn't seem overly bothered by logical chronology in the adventures, as seen when he inserted a playful plug for Destination Moon into the 1950s colour re-draw of Cigars of the Pharaoh, an adventure that even in this 1950s version is still visibly set in the early 1930s.
I agree with you about Alcazar's reversed aging. He seems to shift from one Latin American archetype to another in each book he appears in - bombastic dictator, shady emigré, Ché-like guerrilla - and as you say, each one seems younger than the one before.
