You’re conflating target version with minimum supported version.

There aren’t requirements to update the minimum. They’re independent. There might be limitations on what APIs are still available though in Xcode if they’re removed after a deprecation period however.

You can use the latest SDK, and if you don’t use any new APIs, your app will continue to deploy to whatever minimum you have set.

If you want to use the new APIs, you can put their use behind availability checks.

It’s just that at some point, as a dev, you want to stop testing on older devices and you want to stop branching your code for OS versions that are a minuscule fraction of the active user base. The ROI changes quickly.

Xcode occasionally bumps the minimum will compile for without complaint.