Yeah, that happened to me too. So I decided to delete The Weather Channel app and see what happens. I'm then told that I don't have any app called iPhone. After reinstalling the app the same 'bug' happens.
After trying variations on "am I eligible for an iPhone upgrade" I found that I could get the weather channel to open after asking as little as "eligible for iPhone."
Here's my guesses:
1. The app's name as seen by the OS includes the word "iPhone" and Siri is mis-hearing "eligible" as "channel" and is helpfully opening The Weather Channel for you. I have no other apps with the word "channel" in it so
, maybe?
2. The Weather Channel has a little Siri joke arranged with Apple. When you ask if you're eligible for the upgrade, the app is letting you know what the weather is like so you can decide whether or not you want to go stand in line for the new iPhone. 🙂