The example you provided help clarify very well, thanks. Siri sends that type of question to Wolfram Alpha, part of its heritage. So it does involve some type of internet interaction.
Nonetheless, you may wish to offer your feedback to Apple. Here's how to do that:
Again, there are a few things Siri knows how to do directly, like give you a stock quote, a sports score, weather information. The rest will involve web searches and Siri will tell you about that. That's how it works today.