Show "Designed for iPad" Run Destination

As far as I can tell, the option in question simply allows developers to test the iPad arm64 app natively on their M1 Mac.

In fact, if you hover your cursor over that option in Xcode, you'll see a note: "Only available on Macs with Apple silicon".

Straight from the Mac Catalyst documentation:

The option Show Designed for iPad Run Destination allows [your xcode project], as an iPad app, to run “as-is” on Apple silicon Macs. This requires macOS 11 and a Mac with Apple silicon.

It's worth noting that this option doesn't seem to have any to do with your app's availability to end users. By default, iOS apps are available to anyone running a Mac with Apple Silicon unless you opt-out your project in App Store Connect
(see documentation):

After you sign the updated developer agreement, the App Store automatically makes compatible iOS apps available to users of a Mac with Apple silicon. However, if you’re already planning to ship a macOS version of your app, or if your app doesn’t make sense on the Mac, you can change your app’s availability in App Store Connect.

All that said, I don't have an M1 Mac to test, and so I haven't tested this feature for myself. I welcome anyone to provide more insights.