Following release of iOS 17.0.3 Apple stopped signing iOS 16.6.1 preventing future downgrades. The only previous release which is currently being signed is 17.0.2 (but developers should expect that this is not for long).
Reference: Downgrading an iPhone From iOS 17 to iOS 16 is No Longer Possible
Recommendations
Developer:
Prevent devices from updating, if older releases are needed for development.QA engineer:
Prevent devices from updating, if older releases are needed for testing.PM/DM:
Business as usual.