Apple Ventura 13.21 actively blocks installation of previous 13.x versions
Just left the Genius bar and got the word that there is no way to ever regress the OS. The recovery os auto updates to the newest version and requires internet to initiate installation.
3 comments
[ 3.0 ms ] story [ 28.9 ms ] threadHere is a log of the installer when I attempt:
Device is unsupported: BIPreflightError - Domain: com.apple.BuildInfo.preflight.error Code: 9 UserInfo: {
What I know for sure is that Reduced Security mode turns off the online "phone home" check you described in the OP, but I don't actually know what issue you're encountering.