With Safari 16.3 installed on my Mac, I first tried unsuccessfully to download Safari 16.3.1 on a 2018 Mac Mini with macOS Monterey 12.6.3 installed, then again after upgrading to macOS Ventura 13.2.1. When I searched for this problem I could find nothing but an article on jamf Nation Community's website named "Safari 16.3.1 Standalone Installers" that might be describing why I'm having this problem. It reads "Apple's Security update bulletins published today are calling it Safari 16.3.1, however Apple actually released new builds of Safari 16.3 with updated build numbers so you'll have to use an EA to extract the CFBundleVersion string from the Safari app bundle to figure out exactly what version of Safari you have installed". I guess it's just the two of us.