I think the is rather that there's no pre rendering of the tiles serverside, even dynamically. Its all client side. Ie, updates should just require a dataset update, not a regeneration of map tiles for a tile store in the case of pre rendering. And no need for a spatial server.
Judging from the data requested, there are essentially either prerendered blocks of data, or they're live API calls. So there's still a data transform step.
The data that's coming down looks to be bigger than I'd expect for a PNG tile.
On the other hand, it's a pretty cool way to do a multiband raster.
