Yes, but still if you have somebody looking over your shoulder, it can leak whatever you've been looking at.

There's a way to block that entirely for "secure' apps, but iOS could be smarter about this, and cache some stripped down view or expire that cache quicker.

This is also the case for FaceTime; The last image the camera captured will stay visible in the app switcher like forever... so other people who use your iPad / iPhone can see it.

Yes. Something like that, but can reveal a lot of the site you were in.