I got it working by creating a custom login.php in my theme's folder, but it is disturbing to me that I couldn't make this work. I even moved the site back to root to see if that made a difference, and it still didn't work.
From site_theme_paths:
<?phpdefined('C5_EXECUTE') or die("Access Denied.");$v= View::getInstance();$v->setThemeByPath('/login',"movie_trivia");/*
you can override system layouts here - but we're not going to by default...
view.php:
<?phpdefined('C5_EXECUTE') or die(_("Access Denied."));$this->inc('elements/header.php');?><?phpecho$innerConent;?>
</div>
</div>
</div>
</body>
</html>
I know it's sloppy closing tags I opened in my header include, but whatevs...