Unnecessary condition used in Index Condition Pushdown

EXPLAIN SELECT MIN(b), MIN(c) FROM t1 WHERE a = 1;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ref	a	a	5	const	2	Using index condition

analyze format=json

SELECT MIN(b), MIN(c) FROM t1 WHERE a = 1;

ANALYZE

{

  "query_block": {

    "select_id": 1,

    "r_loops": 1,

    "r_total_time_ms": 0.0893,

    "table": {

      "table_name": "t1",

      "access_type": "ref",

      "possible_keys": ["a"],

      "key": "a",

      "key_length": "5",

      "used_key_parts": ["a"],

      "ref": ["const"],

      "r_loops": 1,

      "rows": 2,

      "r_rows": 3,

      "r_total_time_ms": 0.0462,

      "filtered": 100,

      "r_filtered": 100,

      "index_condition": "1"

    }

  }

}