However, it is possible to alter this behavior and stash untracked files with the right git stash save and push options. The trick is to use the --include-untracked option or for brevity, the -u alias ...

Source: How we improved push processing on GitHub GitHub revamped its code push process by breaking down the long, sequential job into multiple independent, parallel processes.

GitHub has enabled push protection by default for all public repositories to prevent accidental exposure of secrets such as access tokens and API keys when pushing new code.