I'll split that into two parts, I guess.
One, when the application gains the foreground and is able to execute, they can reload the content, if they see fit to reload the content. At that point, you've transferred control to that application, and it will be able to execute and reload, if you'd like.
It's our goal, actually, to minimize those reloads as part of the user experience. It's also our goal that the application currently in the foreground should get, within a sandbox, within a set of limitations we have, the maximum execution and other resources of the device. This can mean that the operating system will remove some of the resources of background applications.
In terms of the reloading that you're seeing, iOS, our operating system, could contribute to that, but fundamentally, regardless of what resources are preserved for that background application, when you transition back to an app, it has execution control and it can reload if it sees fit.