Products added without variation selected

I’ve linked an example product, but this seems to happen with any product.

When customers click on the PayPal button for products with variations, it immediately goes to PayPal checkout, even if a variation option has not been selected. For instance, if a product has different color options, it can be added to the cart even though no color has been picked.

I’m not sure if this is a bug or an option on the backend I’m missing. How can I force the customer to select a product option first, before they can add to Paypal? Basically, making it function the same as a normal WooCommerce “add to cart”

The page I need help with: [log in to see the link]