[MidnightDraven]

Firstly, a data plan gives you service books.
These service books allow access to Blackberry services.
When connected to wi-fi only (with mobile network unchecked BUT data services: ON) it still connects to BIS through wi-fi.
This is the way a blackberry works.
Wi-fi on blackberries, and connecting to blackberry services, is so you can use the wi-fi instead of your data plan MB's incase you are on a pay per use, or low MB plan.
It is also a faster connection for using apps and browsing the internet.

Thats why.

You basically didnt read the article correctly.