Yes, most of the components and files in a default Windows installation are built from sources in the main Windows OS git repo.
Some parts of Windows have split out into their own repos and CI build and test pipelines, but splitting is a process that takes people's time and has pros and cons, especially when changes in the main OS repo are needed to give the separated components a complete, coherent API surface.
"We support SQL on our distributed data platform" has to be the new big lie of distributed systems salespeople.
I'm not saying that computing joins, aggegates, sorts, etc can't be done in a distributed fashion, it just takes time, a lot of network reliability/reattempts, and understanding of the approximate nature of results if there are ongoing "eventually consistent" updates rolling through the cluster(s).
https://github.com/sigstore/sigstore-website