Apple uses a developer beta testing program for its software updates, but the process is changing. Before a software release is made public — like iOS 16, for example — it undergoes a series of beta testing processes. The first period occurs internally at Apple and is used to develop new features and discover any potential flaws. The planned software release then makes its way to developers, who use the beta version to update their apps and identify bugs. Next, public beta testers can sign up to be the first users to test an upcoming software release before it makes its full public debut.
https://screenrant.com/apple-ios-developer-beta-testing-program-changes/