Is it not live yet? The article uses the present progressive "is activating", but e.g., https://whatever.scalzi.com serves a certificate whose CN is *.wordpress.com (i.e., one that is invalid for the intended domain).
whatever.scalzi.com is on WordPress.com VIP—same platform, but a different segment of users. Our VIP sites often use 3rd parties (mostly ad servers) that don't yet support https, so we haven't defaulted any of those sites to https—it's an option available if they want it though!