From the article: "we had to teach Siri to add tasks to Remember The Milk [...] and we're super excited to announce that we've done just that!"
If you leave out that bit, then you're correct, they were claiming they taught Siri to add events. But that bit is important.
From the article: "we had to teach Siri to add tasks to Remember The Milk [...] and we're super excited to announce that we've done just that!"