ALGORITHM=INSTANT fails because of surprise change of timestamp type

MariaDB [regressiondb]> show create table testAndSuite_status\G

*************************** 1. row ***************************

       Table: testAndSuite_status

Create Table: CREATE TABLE `testAndSuite_status` (

  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,

  `topo_id` int(10) unsigned NOT NULL,

  `vmTopo_id` int(10) unsigned NOT NULL DEFAULT 0,

  `extraKey_id` int(10) NOT NULL DEFAULT 0,

  `testAndSuite_id` int(10) unsigned NOT NULL,

  `status` enum('PASSED','FAILED','SKIPPED','UNKNOWN','OUT','GHOST') COLLATE latin1_bin NOT NULL DEFAULT 'GHOST',

  `rotten` tinyint(1) NOT NULL DEFAULT 0,

  `duration` varchar(45) COLLATE latin1_bin DEFAULT NULL,

  `regressRun_id_Pass` int(11) DEFAULT NULL,

  `regressRun_id_Fail` int(11) DEFAULT NULL,

  `origin` enum('scanResult','scanGash','admin','gui','expand') COLLATE latin1_bin NOT NULL,

  `registered` tinyint(1) NOT NULL DEFAULT 0,

  `changedDate` timestamp NOT NULL DEFAULT current_timestamp(),

  `remarks` varchar(140) COLLATE latin1_bin DEFAULT NULL,

  `passCount` int(11) NOT NULL DEFAULT 0,

  `failCount` int(11) NOT NULL DEFAULT 0,

  `bossKey` tinyint(1) NOT NULL,

  `aggregate` int(2) NOT NULL DEFAULT 0 COMMENT '0=normal, 2=agg, 1=pointing to agg',

  PRIMARY KEY (`id`),

  KEY `testAndSuite` (`testAndSuite_id`),

  KEY `topo` (`topo_id`),

  KEY `regressRun_id_Fail` (`regressRun_id_Fail`),

  KEY `regressRun_id_Pass` (`regressRun_id_Pass`),

  KEY `rotten` (`rotten`),

  KEY `extrakey` (`extraKey_id`),

  KEY `vmTopo_id` (`vmTopo_id`)

) ENGINE=InnoDB AUTO_INCREMENT=2717022889 DEFAULT CHARSET=latin1 COLLATE=latin1_bin

1 row in set (0.000 sec)

MariaDB [regressiondb]> alter table testAndSuite_status ADD master_tas_id INT(11) UNSIGNED NULL DEFAULT NULL, ALGORITHM=INSTANT;

ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY

MariaDB [regressiondb]> select VERSION();

+--------------------+

| VERSION()          |

+--------------------+

| 10.4.6-MariaDB-log |

+--------------------+

1 row in set (0.000 sec)

MariaDB [regressiondb]> show variables like '%row_format%';

+---------------------------+---------+

| Variable_name             | Value   |

+---------------------------+---------+

| innodb_default_row_format | dynamic |

+---------------------------+---------+

1 row in set (0.002 sec)