Multi-tasking question

I just installed 4.2 and I'm unsure if multi-tasking is really working or not...

For example, I'm playing Plants and Zombies and I double click the home button and open Safari. Safari opens and I look at a website. I double click the home button again and select Plants and Zombies, but instead of being where I left off, it actually reopens the game like its a fresh start.

I'm noticing the same when I alternate between Friendly and other apps.

Is this becase the apps haven't been properly configured by the developer for 4.2 or is this just how multi-tasking works?

Yes, I'm a newb.

 

Thanks TEG