Wrong result upon GROUP BY with orderby_uses_equalities=on

CREATE TABLE person (

  PersonID MEDIUMINT(8) UNSIGNED AUTO_INCREMENT,

  FullName VARCHAR(100),

  Furigana VARCHAR(100),

  Sex ENUM('M','F'),

  HouseholdID MEDIUMINT(8) UNSIGNED DEFAULT 0,

  Relation VARCHAR(6),

  Title VARCHAR(6),

  CellPhone VARCHAR(30),

  Email VARCHAR(70),

  Birtdate DATE DEFAULT '0000-00-00',

  Country VARCHAR(30),

  URL VARCHAR(150),

  Organization TINYINT(1) DEFAULT 0,

  Remarks TEXT,

  Photo TINYINT(1) DEFAULT 0,

  UpdDate DATE DEFAULT '0000-00-00',

  PRIMARY KEY (PersonID),

  INDEX(Furigana),

  INDEX(FullName),

  INDEX(Email),

  INDEX(Organization,Furigana)

) ;

CREATE TABLE percat (

  PersonID MEDIUMINT(8) DEFAULT 0,

  CategoryID MEDIUMINT(8) DEFAULT 0,

  PRIMARY KEY (PersonID, CategoryID),

  INDEX (CategoryID)

) ;

CREATE TABLE action (

  ActionID MEDIUMINT(8) UNSIGNED AUTO_INCREMENT,

  PersonID MEDIUMINT(8) UNSIGNED DEFAULT 0,

  ActionTypeID MEDIUMINT(8) UNSIGNED DEFAULT 0,

  ActionDate DATE DEFAULT '0000-00-00',

  Description TEXT,

  PRIMARY KEY (ActionID),

  INDEX (PersonID),

  INDEX (ActionDate),

  INDEX (ActionTypeID)

) ;

INSERT INTO person (PersonID) VALUES 

(58),(96),(273),(352);

INSERT INTO percat VALUES 

(58,9),(273,1),(273,9),(273,14),(352,1),(352,13);

INSERT INTO action (PersonID, ActionTypeID) VALUES

(58,3),(96,3),(273,3),(352,3);

SELECT person.PersonID,

GROUP_CONCAT(CategoryID ORDER BY CategoryID SEPARATOR ',') AS categories

FROM person LEFT JOIN percat ON person.PersonID=percat.PersonID

WHERE person.PersonID IN (SELECT PersonID FROM action WHERE ActionTypeID=3)

GROUP BY person.PersonID;

DROP TABLE action, percat, person;

SELECT person.PersonID,

GROUP_CONCAT(CategoryID ORDER BY CategoryID SEPARATOR ',') AS categories

FROM person LEFT JOIN percat ON person.PersonID=percat.PersonID

WHERE person.PersonID IN (SELECT PersonID FROM action WHERE ActionTypeID=3)

GROUP BY person.PersonID;

PersonID	categories

352	1,1,1,1,13,13,13,13

SELECT person.PersonID,

GROUP_CONCAT(CategoryID ORDER BY CategoryID SEPARATOR ',') AS categories

FROM person LEFT JOIN percat ON person.PersonID=percat.PersonID

WHERE person.PersonID IN (SELECT PersonID FROM action WHERE ActionTypeID=3)

GROUP BY person.PersonID;

PersonID	categories

58	9

96	NULL

273	1,9,14

352	1,13