Yeah, so I watched a teardown from one of the sibling comments. Looks like there are vents underneath, but no fan (which would have ruined it for me). Turns out it's got both a huge heat spreader and a newer version of the Broadcom SOC. That's really interesting, because it means they've got the bugs ironed out to be able to do a better pi 4 board which isn't so finicky about its enclosures. And that means I could potentially upgrade the pi 3 that's currently sat in my dusty workshop without caring about fans getting clogged. (yes, I know there are passively-cooled pi 4 cases about. They don't quite do it for me.)