That’s not how it work for mobile platforms. Developers usually set the targets correctly, so incompatible devices can’t install the app, rather than relying on the users to read some text in some website (not appstore where they install it).
AFAIK you cannot set arbitrary compatible devices. You can only set UIRequiredDeviceCapabilities, which are quite limited[0]. There is a required capability for `iphone-ipad-minimum-performance-a12`, but not for A13.
And also if you already have the app in the App Store, you can only relax these requirements. You cannot add new ones as that could prevent users who already bought the app from launching it.
BTW the minimum requirements are listed in Queryable's App Store description as well, although I would consider putting them on the very top.