Simple question... iPhone apps syncing with iPad

Using the iCloud, apps I download on one device are supposed to automatically install on my other ones. I turned those features on, but it doesn't seem to be happening for me. For example, I just downloaded Google+ for my iPhone, but it did not install on my iPad. Is this because the app isn't made for iPad? Does an app have to be universal (with that + in the store) for it to sync from iPhone to iPad? Hope that made sense. Thanks in advance!