Eligibility Rule in Configurator not firing instantly

 Hi - We have set up a few 'Not Available' Eligibility Rules to prevent the selection of a products in a configurator session if the values of a field on the Quote Header (Field Name: Sytem Type) is selected to a particular. We have set the 'Inclusive Eligibility' flag on the Products to be excluded to "N". 
Assuming we have the System field on Quote set to a value that will exclude a bunch of products in a CP: When we customize the product, we observe that the 'Not Available' product do appear in RED, however the selection of the products doest no raise any Eligibility error. No message is prompted even when the Done button is invoked on the configurator session.