People confuse theoretical with practical. Apple tells us it's not necessary. It is. Removing apps from the recently used apps list frees resources. Lots of discussions on this.
A contradiction from the linked article (emphasis mine):
"From there, a Suspended app remains in the devices onboard memory so that it can be quickly launched again (sort of like how Mac OS X Lion handles apps now). Contrary to popular belief, the Suspended state does not use your devices system resources or battery life. If there are too many apps in the Suspended state, iOS is smart enough to purge unnecessary suspensions and move apps to the Not running state."
If they are not using resources there is no reason to purge. But they are purged to free resources when entering a Low Memory condition so they are using resources.
So you can wait for a low memory condition so iOS purges apps or you can close them yourself. Apple does not mention what the user experience is in a low memory condition. However, I can when I pick up my kid's iPod with over 50 applications in the recently used app list. It ain't good.
There's a reason developers tell you to close apps or restart your device when their large applications don't load.
Honestly this post just shows that you don't know what you are talking about. It isn't using system resources because it isn't taxing any part of the system. RAM takes the same amount of power to store a static bit of data as it does to store "no" data (hint there is no such thing). Free ram is a 100% pointless thing to have. Striving to have more free ram is striving to waste more money.