This snippet will override the default published date for the Total Post Types Grid builder block to instead display the last modified date.
add_filter( 'vcex_post_type_grid_date_inner', function( $date ) {
if ( get_the_date( 'U' ) !== get_the_modified_date( 'U' ) ) {
$date = 'Last updated on ' . get_the_modified_date( get_option( 'date_format' ) );
}
return $date;
}, 10 );