Inconsistency between ALTER from BIT to VARCHAR and from BIT to TEXT

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a BIT(8),b BIT(8));

INSERT INTO t1 VALUES (123,123);

ALTER TABLE t1 MODIFY a TEXT, MODIFY b VARCHAR(10);

SELECT * FROM t1;

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

| a    | b    |

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

| {    | 123  |

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