It’s remarkably common for some floating UI element to obscure the bottom portion of something scrollable. You can’t work around this by scrolling because, if the region in question is on the screen at all, it’s at the bottom.

Even Mobile Safari messes this up on occasion — sometimes the URL bar at the bottom obscures the bottom of a page, and, while one can temporarily reveal it by dragging up, the content rubber-bands right back down when the user lets go.