Android PGO profile generation jobs are run with
browser.tabs.remote.autostart = false. We still launch content processes, I assume because e10s being fully disabled isn't a supported configuration nowadays. But this prevents us from launching a GPU process, meaning we don't get profile data from the GPU process.
I think e10s is disabled in testing/profiles/unittest-required/user.js. On desktop that is then overridden here, but deliberately not so on Android. I presume that's simply because enabling it for desktop PGO runs predates e10s being enabled generally on Android.
I think the solution is to remove the override from desktop-specific
profileserver.py, and instead set the pref to true in
testing/profiles/profileserver/user.js, which is used for both desktop and Android.