Well, I don't know how their backend processes are set-up. If you do, then fine, I'm wrong. In fact, I fully expect that I am wrong. It's more reasonable than you're giving credit (I've seen this kind of thing in practice), but I don't care to defend it because... I'm sure you're right: I'm wrong.
The point of that scenario isn't to say "this is exactly what happened," the point is to illustrate that there are unknowns which could easily undermine the alphabet/achievement clue. And I think it's worth considering, that's all.
I admit this is an inference on my part based on my experience with the DLC system - there can often be very little time between work apparently begins on a DLC and the addition of achievements.
Either way, it makes no sense to settle on the achievements until enough of the game is finalised to know which achievements will be in - a civ that's taken out of the game doesn't just create one 'achievement gap', almost every civ has at least one other achievement beyond "win the game" specific to that civ. We also have no reason to believe the Pueblo were the only civ removed from BNW in the planning stages - they were explicitly described as an
example of the way civs can be removed during the game design process. Similar things have probably happened in prior expansions with no 'achievement gaps' resulting.
EDIT: Somebody's suggested the Celts are out of place in the G&K order, however it strikes me as unlikely that the Celts would have been a 'substitute' civ since they're a returning civ that fits the game's theme, so the explanation there is quite likely different.
I'd like to point out that none of the leaders revealed so far for BNW have been female. G&K was heavy on females, but I would find it pretty unlikely that BNW would not have at least one female leader. I think we can use this fact to narrow down the choices for the last civs.
it's been noted that they have Maria. We know they'll stretch to get a female leader if a civ they've chosen has a possible option (see Maria), but that doesn't imply that whether there's a female leader factors into their decision when including a civ. I'm not sure there are any civs in Civ IV you can point to and say they're unlikely to have been considered if they have no possible female leaders.
The general consensus for the main two remaining European civs are Italy and Hungary. To my knowledge, there are no notable female leaders for either civ.
Hungary seems unlikely - it doesn't explain the apparent absence of Venice from the BNW CS list, and it's been suggested that Bratislava may rule it out.
I am not familiar with any notable female Native American leaders (they really wouldn't put Pocahontas in would they? Just....no.)
Irrelevant. The inclusion of a Native American civ has the strongest evidence of any option for the final three civs, since we've seen a unit with a Native American graphic. We don't know why it's been seen with barbarian colours, but it's too specific not just to Native Americans but to a particular group of Native Americans to plausibly be a generic barbarian unit. This is the only evidence we have for any unique associated with any of the three remaining civs, with the more ambiguous exception of the motte and bailey (which has not been seen in any actual gameplay screenshot).
So, we must ask, who are civs being talked about that have a notable female leader? Only one immediately comes to mind: Vietnam. The Trung Sisters are national heroes for Vietnam and it would give Firaxis an opportunity to do something they've never done before to my knowledge: Have two leaders in one leaderscreen.
Indonesia apparently also has notable female leaders from what's been said in past threads, though I don't recall who.
I still think we may be dismissing the "joke" about the definition of European civs too readily. We were asked "what do you mean by European?" with the options:
European civ: Venice or Italy likely.
Eurasian landmass: Possibly a reference to Morocco, a non-European civ culturally with territory in Iberia.
Culturally European: No suggestions. But if the other two 'teasers' are taken, this one might be. Considering a Native American civ as being culturally European is a stretch for any time period we'd expect Native Americans to represent (unless perhaps the civ is the Cherokee). That seems to leave the mystery civ. Colombia is contentious, but may fit the alphabet. Canada is less contentious and also fits. The Philippines would add an Asian civ, and fills in part of the SE Asian geographic gap while fitting the "culturally European" criterion to a degree, but would be a truly bizarre choice.