MySQL Query Optimizer Ingoring Index no Timestamp

Eu tenho a seguinte tabela:

CREATE TABLE `matches` (
  `id` char(32) NOT NULL,
  `borrower_id` int(10) unsigned NOT NULL,
  `product_id` int(10) unsigned NOT NULL,
  `category_id` int(10) unsigned NOT NULL,
  `lender_id` int(10) unsigned NOT NULL,
  `classification_id` int(10) unsigned DEFAULT NULL,
  `status` enum('accepted','partial','potential','rejected') CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
  `classification` varchar(255) DEFAULT NULL,
  `category` varchar(255) DEFAULT NULL,
  `lender` varchar(255) DEFAULT NULL,
  `product` varchar(255) DEFAULT NULL,
  `created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  KEY `borrower_id` (`borrower_id`,`product_id`),
  KEY `status` (`status`),
  KEY `created_timestamp` (`created`),
  KEY `borrower_id_2` (`borrower_id`,`product_id`,`created`),
  KEY `borrower-product-classification` (`borrower_id`,`product_id`,`classification_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Quando executo EXPLAIN SELECT COUNT(*) FROM bi.matches WHERE created >= '2016-09-10';, obtenho os seguintes resultados:

| id | select_type | table  | type  |   possible_keys   |        key  | key_len | ref  |   rows   |          Extra                            |

|----|-------------|--------|------|-------|-------------------|------------------|---------|------|----------|--------------------------|      

    1| SIMPLE      | matches | range | created_timestamp | created_timestamp |       4 | NULL | 13288480 | Using where; Using index |

Mas quando eu executo esta consulta:

EXPLAIN SELECT COUNT(*)
FROM bi.matches m
INNER JOIN bi.matches m1
    ON m.borrower_id = m1.borrower_id
    AND m.product_id = m1.product_id
    AND m.created > m1.created
LEFT OUTER JOIN bi.matches m2
    ON m1.borrower_id = m2.borrower_id
    AND m1.product_id = m2.product_id
    AND m.created > m2.created
    AND (m1.created < m2.created OR (m1.created = m2.created AND m1.id < m2.id))
WHERE m.created >= '2016-09-10'
AND m2.id IS NULL
AND m.status = m1.status;

Eu recebo a seguinte explicação:

| id | select_type | table | type |                                    possible_keys                                    |               key               | key_len |               ref                |   rows   |                Extra                 |

|==========================================================================|
|  1 | SIMPLE      | m     | ALL  | borrower_id,status,created_timestamp,borrower_id_2,borrower-product-classification  | NULL                            | NULL    | NULL                             | 75151052 | Using where |

|  1 | SIMPLE      | m1    | ref  | borrower_id,status,created_timestamp,borrower_id_2,borrower-product-classification  | borrower-product-classification | 8       | bi.m.borrower_id,bi.m.product_id |        3 | Using where                          |

|  1 | SIMPLE      | m2    | ref  | PRIMARY,borrower_id,created_timestamp,borrower_id_2,borrower-product-classification | borrower_id_2                   | 8       | bi.m.borrower_id,bi.m.product_id |        4 | Using where; Not exists; Using index |

Por que o MySQL usaria created_timestampna consulta mais básica, mas não quando as junções estão envolvidas?

Também aqui está a saída deSHOW INDEXES FROM bi.matches

|  Table  | Non_unique |            Key_name             | Seq_in_index |    Column_name    | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
|=========================================================================|
| matches |          0 | PRIMARY                         |            1 | id                | A         |    75151052 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | borrower_id                     |            1 | borrower_id       | A         |      434399 | NULL     | NULL   |      | BTREE      |         |               |
| matches |          1 | borrower_id                     |            2 | product_id        | A         |    18787763 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | status                          |            1 | status            | A         |        2232 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | created_timestamp               |            1 | created           | A         |       37075 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | borrower_id_2                   |            1 | borrower_id       | A         |      521882 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | borrower_id_2                   |            2 | product_id        | A         |    18787763 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | borrower_id_2                   |            3 | created           | A         |    75151052 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | borrower-product-classification |            1 | borrower_id       | A         |      478669 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | borrower-product-classification |            2 | product_id        | A         |    25050350 | NULL     | NULL   |      | BTREE      |         |               |

| matches |          1 | borrower-product-classification |            3 | classification_id | A         |    18787763 | NULL     | NULL   | YES  | BTREE      |         |               |