Conversion from TIMESTAMP to VARCHAR SP variables does not work well on fractional digits

DROP PROCEDURE IF EXISTS p1;

DELIMITER $$

CREATE PROCEDURE p1()

BEGIN

  DECLARE ts10 TIMESTAMP(1) DEFAULT NOW();

  DECLARE ts16 TIMESTAMP(1) DEFAULT NOW(6);

  DECLARE dt10 DATETIME(1) DEFAULT NOW();

  DECLARE dt16 DATETIME(1) DEFAULT NOW(6);

  DECLARE vts10 VARCHAR(32) DEFAULT ts10;

  DECLARE vts16 VARCHAR(32) DEFAULT ts16;

  DECLARE vdt10 VARCHAR(32) DEFAULT dt10;

  DECLARE vdt16 VARCHAR(32) DEFAULT dt16;

  SELECT vts10, vts16, vdt10, vdt16;

END;

$$

DELIMITER ;

CALL p1\G

vts10: 2018-12-07 16:19:32

vts16: 2018-12-07 16:19:32.900000

vdt10: 2018-12-07 16:19:32.0

vdt16: 2018-12-07 16:19:32.9