Every element is one of the organization's custom subcategories or one canonical subcategory; a custom shares productSubCategoryId with the canonical it maps to, and a canonical stays pickable beside its customs. The default response is the pickable set only - includeExcluded adds the excluded canonicals, includeDeleted adds soft-deleted customs. includeProductCounts adds productCount, counted direct-only: a custom element counts the products assigned to that custom and a canonical element counts only the products still on the bare canonical with no custom assigned, so a canonical and its customs never double-count and the two can be summed. The count costs an aggregate query, so ask for it only when the caller reads it. productCategoryId scopes the whole response to one category. A flag is enabled by the exact value true - every other value, 1 and TRUE included, reads as false.