As mentioned on the other thread, pointing to the official announcement, the iPhone 5 launched in China on a different date, so it had 2 million sales on its launch there.
So to get the real comparison you need to add first weekend sales of the 4S in standard launch countries and China to that 7 million figure.
That makes the 9 million figure a whole lot less impressive. From 7+ million to 9 million... but it's not that unthinkable that there could have been 2 million iPhone 4S's sold when the iPhone 5 launched, so that it could even be a step down from the previous year.
Apple doesn't break down numbers to the device level. 5M sold last year was 5m combined iPhone sales (all models). So this really is an apples to apples comparison...
So to get the real comparison you need to add first weekend sales of the 4S in standard launch countries and China to that 7 million figure.