Yes, and for what it's worth, I feel Space to page down is another oddball one. I guess it's for the supremely lazy who don't want to have to move their finger to the Page-Down key.
Page-Down means I have to almost move my hand away from the keyboard (middle finger to the top right corner, can't hit it with other fingers because display) -- that feels like grabbing for the mouse...
Historically, space is also the hotkey for 'more'.