The "definition" part of that page is this:
Quote ="RFL"The direction of a pass is relative to the player making it and not to the actual path relative to the ground.'"
All the rest of it, including mention of the receiver, is just illustration. Quite simply, the passer must throw the ball backwards relative to him/herself. Nothing else matters. It really is that simple, and all mention of players speeding up, slowing down or getting tackled or not, is just confusing the issue.