Wordpress - CMB2 metabox conditional logic

You need to replace the get_option call with a call to get_post_meta:

function show_this_field_if_true( $cmb ) {
    // Check if other meta value exists
    if ( ! get_post_meta( $cmb->object_id, 'other_meta_key_to_check', 1 ) ) {
        return false;
    }
    return true;
}

Keep in mind, this will only work for the initial page-load and will not show the field until you update the other_meta_key_to_check value and save the page.