This question, "Size of “Weekly Export” vs. “Data Storage” is different, why?" - was flagged as a dup, but it clearly is not a dup in my opinion. Updating the other question & answer to account for my question in my opinion makes no sense either, nor would it make sense to cross post the answer posted to my question to the other question, since it would address a question not asked by the other question; though the link has been updated on the other question thanks to Daniel Ballinger who has also posted an answer which I accepted on my question.
I on the other hand did vote to keep the question open, and not closed as duplicate. I think it does have a more specific scope that warrants a specific answer. I fully agree with ca_peterson's reasoning about closing/linking duplicate questions when they they can roughly be answered the same. This promotes a single question with answers combination which is easier to update or reference over time.
Though often this can be somewhat subjective, I'm afraight you are then handed over to the "mercy" of the community. If duplicate votes start happening, you do well to update your question to explain why you think it is different. I think you've handled that rather well with your question.
While not an identical question to me it's substantially similar once you understand how storage is calculated in salesforce. The principal point is that actual data has no bearing on how salesforce calculates storage, which is addressed by the question I flagged yours as a possible duplicate of.
The leap from the concept "physical space != sfdc space" to "why is my data export differently sized than what sfdc shows?" seems like a rather small leap to me. At it's core the same logic applies to answer both situations - physical disk size of exports is just a downstream implication of salesforce using non-physical data calculations.
One of the things that makes me love the stackexchange model so much is that it tries to build up quality questions and answers that get re-used for common topics, meaning that more attention on a central "why is storage all weird?" question is actually beneficial on the whole as it centralizes discussion and dissent there, and in the event it changes in the future we'd only have one question that needs to note the change. With that said, flagging your question as a possible duplicate wasn't a criticism of it - the way it's handled is certainly non-intuitive.
Finally, thanks for taking this conversation to meta, a much better place for it than the comments on your question!