A question that deals directly with what has happened in our real world and has no speculative elements does not seem to me to be directly related to the subject of world building.
Instead, it seems to be more like background research. Which is a great thing to do, but isn't something a worldbuilding expert would be the most likely to be able to help out with.
Given this, a question that prompts the use of your proposed tag should in my opinion be asked on the History Stack Exchange. Or, depending on the specific subject matter, any of the myriad other science-based sites in the network. (What we can add here is largely the "what would happen if this happened" part; if your question is "please describe this part about this real-life thing" then ours is likely not the best place to ask the question.)
On our site, I would argue that it should probably be voted to be closed as not worldbuilding, and if it's a good question I could see benefit in it being flagged for possible migration to History SE or elsewhere.
Conversely, a question that asks whether a concept is feasible as well as for similar things done in the real world, without necessarily being about exactly what has happened in our real world, seems well served by the existing science-based and reality-check tags, in combination with a specific subject tag (such as for example history). Such a question, generally speaking, would appear to be more on topic here than on say the History SE, because of its speculative elements.
TL;DR: Let's not abuse tags and turn them into what they were never really meant to be in the first place.