Address validation error on add to cart

When using EVENT_DEFINE_RULES in module adding items to cart fails as address validation is run.

Should address validation only happen when address fields are present in the post data to ‘commerce/cart/update-cart’ or when progressing to payment as it is normal practice for users to add items to cart before submitting a shipping address.

module function;

Event::on(
            Address::class,
            Model::EVENT_DEFINE_RULES,
            function(DefineRulesEvent $event) {
                $rules = $event->rules;
                $rules[] = [['firstName', 'lastName'], 'required'];
                $event->rules = $rules;
            } 
        );