EAS Update does not support percentage-based rollouts. With that said, we built EAS Update with percentage-based rollouts in mind. We plan to work on rollouts in 2023. With this feature, you'll be able to incrementally roll out one update over another to a percentage of your end-users.
To deploy updates safely, check out our guide on deployment patterns. By testing changes before updating end-users, we can significantly reduce the chance of shipping breaking changes. With that said, stay tuned to our blog and to our Twitter for updates on rollouts.