Unexpected error when create table with SELECT JSON_KEY_VALUE

SELECT JSON_KEY_VALUE('{"a":1,"b":22}', '$') AS direct_value,

       CHAR_LENGTH(JSON_KEY_VALUE('{"a":1,"b":22}', '$')) AS direct_len;

-- [{"key": "a", "value": 1}, {"key": "b", "value": 22}]   53

CREATE TABLE t_key AS

SELECT JSON_KEY_VALUE('{"a":1,"b":22}', '$') AS c;

-- ERROR 1406 (22001) at line 8: Data too long for column 'c' at row 1