I'd add this as an answer, but it turns out utf8 vs utf8mb4 was the issue.

I bailed on this, having opted to go a different route (creating a custom module, doing db_query and using hook_menu + hook_theme to get the same results). In the event that somebody comes up with something clever, insightful, etc. I'll leave this open for a bit longer.

I can confirm the comment about the missing UI element re: linking, and the subsequent "no longer seems to work" added by @thirdender... though in this case the grouping I'm using might be throwing things off (tests in output as a field seem to confirm it doesn't work though).

Can I make a Views “Rendered Node” field not be linked to the original node? looks promising. (I've got jQuery Update installed, so my Views UI doesn't alway ring true. I'll have to double check my options.)

Thanks @bloke_zero! I think you're probably right. I was hoping for something a little cleaner, but everything I've seen uses block level menus (as opposed to the base Bartik inclusion), so that's another road to go down. I also ran across TB Mega Menu as a fallback (and a good one at that). I just wanted something I could take cross platform (and explain easily to clients...). Not defeated, but reconsidering... Thanks again!

From the theme level, using menu_tree_all_data(), menu_tree_output() and drupal_render() works... i.e. (one-liner: print drupal_render(menu_tree_output(menu_tree_all_data('main-menu‌​'))); ) Just make sure to break things out and use a variable to pass to menu_tree_output() which appears to be expecting a reference... despite what the API says.