Main category shows products instead of subcategories

I’m building a website with multiple layers of subcategories. Categories display OK on all the child categories, but the parent category only displays products.

Eg:

Shop > T-shirts > Small > Red (list of small red t-shirts)

Shop > T-shirts > Small (list of red, blue and green subcategories)

Shop > T-shirts > (list of all products in alphabetical order)

Shop > (list of all base-level categories, eg. T-shirts, Trousers, Shoes)

Small, Medium and Large subcategories each display Red, Blue and Green sub-subcategories, no problem.

Why does the parent category show products instead of subcategories, when subcategories are able to show sub-subcategories just fine?

I’ve tried the archive-product.php <? woocommerce_product_subcategories(array(‘force_display’ => true)); ?> hack but it didn’t do anything. Woocommerce settings are configured as:

Shop Page Display > Show Categories & Subcategories
Default Category Display > Show Categories
The T-shirts category is also configured to display Subcategories instead of the default view.

What’s going on??? Is this a bug or a “feature” of Woocommerce?