The three finger drag pattern comes from Fingerworks, the multitouch trackpad company that Apple bought to get their multitouch tech.

A Fingerworks trackpad is when I switched away from a mouse, and in some ways it was even better than a modern Apple trackpad. First it was huge, maybe like twice the area of a MacBook Pro trackpad. It had no click switch at all. Taps only, which were very reliable.

It also lay flat on the desk and was only a few mm thick. So it felt like just resting your hand on the desk. And it was possible to just passively rest your hand on it with no reaction. So using it, my hand and wrist were totally relaxed when not moving the cursor (most of the time). Whereas with modern Apple trackpads, I sometimes get spurious inputs when resting my hand on it.

It also had tons of gestures that were mapped to keyboard shortcuts. So an “opening the jar” arcing motion with 4 fingers opened whatever file was currently highlighted. And “closing the jar” closed the current window. Etc.