Ransack association not_eq lead to some errors

Question

I'm using ransack for a while and I just realised that using not_eq on an associated search is different and is making a weird NOT IN ... NOT request that seems to lead to error and make it difficult to debug.

Here is the ransack query I do, with the sql request it does

=> account.contacts.ransack(
  g: { 
    '0' => {
      "contact_fields_landing_page_field_definition_id_eq"=> "1432", "contact_fields_value_not_eq"=> "0" 
    } 
  } 
).result.to_sql


SELECT `contacts`.* 
FROM `contacts` 
LEFT OUTER JOIN `contact_fields` ON `contact_fields`.`contact_id` = `contacts`.`id` 
WHERE `contacts`.`account_id` = 1 
  AND (
    `contact_fields`.`landing_page_field_definition_id` = 1432 
    AND `contacts`.`id` 
    NOT IN (
      SELECT `contact_fields`.`contact_id` FROM `contact_fields`
      WHERE `contact_fields`.`contact_id` = `contacts`.`id` 
      AND NOT (`contact_fields`.`value` != '0')
    )
  )

It return 540 contact with this request.

If I use classic activerecord query

=> account.contacts.left_joins(:contact_fields).where(
    "contact_fields.landing_page_field_definition_id = 1432 AND contact_fields.value != '0'"
  ).to_sql

SELECT `contacts`.* 
FROM `contacts` 
LEFT OUTER JOIN `contact_fields` ON `contact_fields`.`contact_id` = `contacts`.`id`
WHERE `contacts`.`account_id` = 1 
  AND (contact_fields.landing_page_field_definition_id = 1432 AND contact_fields.value != '0')

This query give return me a total of 1940 contacts and this is exactly the number I'm looking for.

I don't get why I have such a big difference between the 2 requests