There is no blocking page displayed when a secured (https) website has been blocked by Home Network Security.
This is due to certificate verification process when visiting secured websites. Instead of displaying a blocking page, it will not load the website or sometimes saying page is unreacheable.
Instead of a blocking page, Home Network Security uses push notifications to inform that the website you are trying to access is denied.
Tapping the push notification will show you the Report Timeline with the list of websites blocked by Home Network Security.