To debug, I used a GUILayout.Label() to display the PlayerPref variable assigned to the radio buttons in the UISavedOptions component of their parent object.
When I pressed the radio buttons on my Mac, the correct values were displayed on the screen. On my Android phone, however, I only got an empty string.
I am checking the isChecked property of the checkboxes directly. It works, just not as elegantly as using PlayerPrefs. Once again, it could just be something quirky about Unity/Android.