No. SO was founded by two windows developers, and build on a windows stack. They had a podcast detailing the process of development prior to public release of the site, followed primarily by windows developers.
The initial audience of the site was, ergo, primarily windows developers. As popularity grew, more developers from the broader community showed up, driving the proportion of windows questions down.
Also as the knowledge base of questions for a tag grows, room for new questions become fewer. Duplicates will be asked but I wonder how many times a person has a problem, does a search, finds an answer and never has to ask their own question on the topic.
Unfortunately breakdown for the close votes is not available like for the flagged answers. But my experience with the review queue is that 1 in every 4-5 votes is due to a duplicate.
Considering there are 58.1k close votes to review at the moment... that's loads of dupes.
The initial audience of the site was, ergo, primarily windows developers. As popularity grew, more developers from the broader community showed up, driving the proportion of windows questions down.