I think it’s because they’re using the custom menu in the header widget area, and you’re using the primary menu.
You should be able to remove it by adding this code to your landing page php file –
remove_action( 'genesis_after_header', 'genesis_do_nav' );
Or you could just use css to have it removed visually by adding this –
.epik-landing .head-wrap {
display: none;
}