In the user study, it would be convenient if the users don't have to manually set the flags.

One solution is to use Finch, but Finch config doesn't differentiate Alpha channel users (yet?), so we have to use a fragile and error-prone way to specify the version range in the config file, with the possibility to negatively affect the real experiments underway if the config files are not updated correctly in coordination with the release schedule.

The alternative is to force the behavior downstream, and discard Finch settings locally. This approach is more localized, but it seems hard to NOT discard flags while discard Finch. It should be fine if these features cannot be overridden in chrome://flags, since that would break the UI for the targeted user study anyway.