Merchandising rules are not applied to the facet "productClusterIds". This happens because this facet has the special behavior of sorting the products by the collection order instead of relevance and merch rules.

This facet should not be considered valid for a merch rule.

• create a collection with some products in a specific order
• create a merch rule explicitly filtered by "productClusterIds" or "productClusterSearchableIds"
• set this rule to sort the products in a different order
• check in the store that the products will keep the collection sorting

The expected way to manage and sort products in a collection is to do it directly on the collection by adding/removing products or changing their position.

It's also possible to apply the merch rule to the facet "productClusterNames" instead. This facet follows the relevance rules instead of the collection order and works with merchandising rules.