mysqli and nested transactions

Hi! It seems that nested transactions work correctly using $this->db->trans_start (and the appropriate fix from here https://ellislab.com/forums/viewthread/101648/) but the behaviour it's different when using $this->db->trans_begin

PHP Code:

public function trx_test() {
        $this->db->trans_begin();
        
        $this->db->insert('test_tbl', array('id' => 0));
        
        $this->db->trans_begin();
        
        $this->db->insert('test_tbl', array('id' => 1));

        $this->db->trans_rollback();
        
        $this->db->trans_commit();
} 


test_table contains only 1 row with id = 0

PHP Code:

public function trx_test_2() {
        $this->db->trans_start();
        
        $this->db->insert('test_tbl', array('id' => 0));
        
        $this->db->trans_start();
        
        $this->db->insert('test_tbl', array('id' => 1));

        $this->db->trans_rollback();
        
        $this->db->trans_complete();
} 


test_table contains no rows


Is this difference by design or what? I'm expecting same behaviour (the correct one should be the one from trx_test_2).