The nearest thing you could compare the development model to is the set of base packages for the BSDs: each subsystem/package has its own upstream development (like the Linux subsystems with their maintainers); and then Linus serves as the release engineer, taking updates to those packages and merging them into the release. (I compare to the BSDs specifically because Linux kernel subsystems, like non-cross-platform BSD base-system packages, have no other life outside of their potential integration into the release. People aren’t using the upstreams directly, other than in development of the new feature.)
So I don't think raising the way linux uses git by its original intended users really contradicts the idea that it was designed for a large number of developers?
Are there really ten thousand active developers on the Linux Kernel?
According to [1] there were ~ 2,000 over a 15 month period. It's an order of magnitude difference that seems like it would have an impact.
[1] https://arstechnica.com/information-technology/2015/02/linux...