Ah. The submenu links, in this particular case, are actually on-page anchor links for the current page.
For example, the parent is:
http://clients.werremeyer.com/wgsd/thematic-goals/
And the submenu Culture of Innovation link is:
http://clients.werremeyer.com/wgsd/thematic-goals/#culture-of-innovation
As a test, I replaced the links from the first two submenu links with a #. Those links now appear as intended because their parent element li’s aren’t being given the class “current-menu-item”.
Since this is a highly unique use case, I suspect the theme is not setup to test for an on-page anchor link and differentiate it from the base page link itself. The appropriateness of the “current-menu-item” designation depends on one’s definition of what the “current-menu-item” should be – specifically how granular it should be. I suspect it will be up to me to solve this particular styling challenge with custom css afterall.
Thanks again for your help.