I did some more research. Hueman is actually using the default WP functionality for the excerpt which is, if there is a user-defined excerpt, return that unchanged, otherwise return a automatically generated trimmed-down version of the full post content which has all shortcodes and tags removed. So, that explains why the shortcode shows up as part of the content in a user-defined excerpt, but gets stripped out of the excerprt that is automatically-generated from the post content. If you’re interested in the specifics, here is the Codex reference for “the_excerpt” function that Hueman uses.
The fix is to override the default functionality with a user function to strip the shortcodes but keep the content, which I found here:
function custom_excerpt($text = '') {
$raw_excerpt = $text;
if ( '' == $text ) {
$text = get_the_content('');
// $text = strip_shortcodes( $text );
$text = do_shortcode( $text );
$text = apply_filters('the_content', $text);
$text = str_replace(']]>', ']]>', $text);
$excerpt_length = apply_filters('excerpt_length', 55);
$excerpt_more = apply_filters('excerpt_more', ' ' . '[...]');
$text = wp_trim_words( $text, $excerpt_length, $excerpt_more );
}
return apply_filters('wp_trim_excerpt', $text, $raw_excerpt);
}
remove_filter( 'get_the_excerpt', 'wp_trim_excerpt' );
add_filter( 'get_the_excerpt', 'custom_excerpt' );
It worked on my test system. Let me know if it works for you.