Non-spatial key on POINT silently changes prefix key length

CREATE OR REPLACE TABLE t1 (a POINT, KEY(a(10)));

SHOW CREATE TABLE t1;

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

| Table | Create Table                                                                                             |

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

| t1    | CREATE TABLE `t1` (

  `a` point DEFAULT NULL,

  KEY `a` (`a`(25))

) ENGINE=InnoDB DEFAULT CHARSET=latin1 |

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