> the only way WEI would prevent bots would be by preventing you from running the browser on an operating system without 3rd party software installed

Or by isolating the browser from third party software. Android does not let applications mess with each other. Windows already prevents non-elevated applications from touching elevated applications (i.e. running as administrator).

What makes you think that Windows won't add an "untouchable" mode to executables belonging to "approved" browsers? The kernel is already locked down so you won't be able to bypass it that easily.