Catalina Keyboard shortcuts preferences missing 'full keyboard access'
The UI was simply changed in Catalina. In Catalina, ticking "Use keyboard navigation to move focus between controls" is identical to selecting "All controls" in Mojave. Unticking "Use keyboard navigation to move focus between controls" in Catalina is identical to selecting "Text boxes and lists only" in Mojave.

You can confirm this using Terminal in both versions of macOS and seeing what changes in the output from defaults read (redirect the output to a file and diff the two files). Switching between the radio buttons on Mojave and enabling/disabling the checkbox on Catelina both only change the following preference:

defaults read "Apple Global Domain" AppleKeyboardUIMode


When "Use keyboard navigation to move focus between controls" is ticked (or "All controls" is selected) the value is 2. When "Use keyboard navigation to move focus between controls" is unticked (or "Text boxes and lists only" is selected) the value is 0.