I feel a bit foolish now. Didn't realize this, but when in the customizer preview, you need to be on the page that the custom widget area is displayed on in order for the section to appear in the customizer Widgets panel.
TL;DR
PEBKAC error 😉
Hey Brad, welcome to Beans Community.
You are correct, the widget area has to be called on the page to have it available in the customizer 😉
Happy coding,