Field type "time" does not render with Field API

Create a module and custom field type with corresponding widget. in the "formElement" function of the widget class; build and return a "time" field type. Ex: '#type" => 'time'.

Expected behavior is to render a time field without date.

Result was no rendered field at the markup level.

This is not server dependent. Tried on multiple environments. Comments in Drupal core indicated "time" is a valid field type.

Errors:
Warning: Illegal offset type in Drupal\Core\Render\Element\Select::processSelect() (line 129 of /var/www/html/docroot/core/lib/Drupal/Core/Render/Element/Select.php).