Most of the divergences are already compile flags or command line flags on upstream. They are just disabling it by default. Is not a Brave-only thing, but different browsers have different settings disabled, the community that compiles the browser from source also pushes those features to be conditionally added. Eg. Debian, Arch or other distros, could have WEI disabled on their chromium distribution, forks like Edge and Vivaldi could disable GAIA, etc.
Just give a look at the divergence issues and the PRs solving them [1], most of them are just single file or small changes to compilation/default flags
Just give a look at the divergence issues and the PRs solving them [1], most of them are just single file or small changes to compilation/default flags
[1]: https://github.com/brave/brave-browser/wiki/Deviations-from-...