Because the steps in that section keep getting passed around as possible fixes. Some of them are mentioned in this very thread. Sadly, it's been my experience that the fix Apple does suggest doesn't work reliably (works for some, not for others), either.
EDIT: holy crap, as toddn points out above, apparently that section is also to contradict the bad information that is passed around in Apple's own KB articles: http://support.apple.com/kb/HT5538
I did all this a few weeks ago but still had to wait a few weeks for my friends' iPhones to realize my number was no longer iMessage enabled. During that time they all had to "Resend as SMS" on their messages to me.
We all ended up on Google Hangouts in the end (the iOS app is nice!)
1. Reset your Apple ID password and do not log back in on your device(s)
2. Send a text to 48369 with the word STOP
It won’t happen immediately but over a 12-hour period, you should start receiving texts on your Android device that are sent from iPhone users.
http://www.techrepublic.com/article/how-to-keep-receiving-sm...