The battery icon on the iPhone with Face ID has been updated to show the specific battery percentage, rather than just a visual representation. The only model with a battery indicator that isn't available on the 12 and 13 models is the mini. It's also available on the newer models of the phone.
The lack of space on either side of the notch that houses the TrueDepth camera hardware is the reason why battery percent isn't present on the Face ID-equipped phones. A better idea of battery status is provided by adding the specific battery level to the icon.
The battery icon shows a visual of the battery level, but it doesn't give a percentage. If you want to see that information, you have to use the Control Center or the Today center view.
The battery icon changes depending on the status of the battery and the wallpaper on the phone. The battery icon is green when it's time to charge.
The battery percentage can beggled on and off in the settings app. The battery percentage feature appears to be available on most phones that have a notch, but it does not appear to be an option on the ones that do not.
Apple will be releasing a public version of the mobile operating system in the near future.