List(text) field not flagging as required when using check boxes / radio buttons

I'm not sure if this is an issue with the theme or with the underlying Drupal core code.

On a new contact form I defined a List(text) field that has three possible values for the user to choose from. I also made it a required field.

On the Manage form display tab, when I choose the Select list widget, on the client side there is a red asterisk next to the field name, indicating that it is a required field. But if I instead choose Check boxes / radio buttons, the red asterisk is not shown. I can switch between widgets and it is consistent in that the indicator is shown for Select list but not for radio buttons.

Luckily, even though the red asterisk is not shown for radio buttons, under the covers Drupal knows it is a required field, and will warn me if nothing is chosen.