Views filter "NOT IN" showing all results

I have a drupal commerce website.

On my product, i've added a field "stock" which tell if is product is available (custom workflow) which is like the "visibility" field (list of all stores with checkboxes).

I've created a view which list all of my product for a specific store (each store is assign to 1 user).

In my view result, I rewrite the value ot stock. If my store is in the product stock list, I show "available" (else "not available") instead of the store IDs list.

So far, everything is great.

I'd like to add a filter with "available/not available". So on my view, i've added the filter "stock", as "group" and I've added 2 options (available/not available)

Now I'd like to "link" the filter with the "stock" field. I've created the mymodule_views_query_alter function to rewrite the condition to match my needs.

But it doesn't work as expected. The "available" option works with "IN/=" (don't get why "=" is working), it doesn't show the . The "not available" options show every row (with NOT IN), even the available rows.

function mymodule_views_query_alter(ViewExecutable $view, QueryPluginBase $query)
{
  if($view->id() == "myview") {
    foreach ($query->where as &$condition_group) {
      foreach ($condition_group['conditions'] as &$condition) {
        if ($condition['field'] == 'commerce_product__field_stock.field_stock_target_id') {
          $current_user = \Drupal::currentUser()->id();
          $stores = StoreHelper::getStoreByOwner($current_user);
          $store = count($stores) ? $stores[array_key_first($stores)] : NULL;
          $value = $condition['value'];
          if($value == "true") {
            $condition = [
              'field' => $condition['field'],
              'value' => "{$store->id()}", //2
              'operator' => 'IN', // works with "="
            ];
          } else if($value == "false") {
            $condition = [
              'field' => $condition['field'],
              'value' => "{$store->id()}",
              'operator' => 'NOT IN',
            ];
          }
        }
      }
    }
  }
}

EDIT : the result ::

The database structure (which means the product is available for the store 4,2,6):

bundle   |entity_id  |field_stock
product  |         38|          2
product  |         38|          4
product  |         38|          6