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That's not how it works. See grapheneos.org/releases#about.
A normal release goes through internal testing, is pushed out to the Beta channel for public testing and then gets pushed out via the Stable channel. Releases not pushed out to Stable are marked as a preview release.
A release in the Stable channel has been through the Beta channel and an internal testing release channel prior to that. The releases page has a list of available releases for both the Stable and Beta channels. You can see exactly what's available through the public channels.