I was playing on a Preview world with the new update experiment(s) turned on and found a village. But when I switched to spectator mode I found, beneath the Village buildings, flat empty spaces with grass blocks placed about every 4 blocks, like a layout grid. There also were those block arrangements on the surface. It seems like those blocks are used for the world-gen Village layout, with each building, and some pathways, having the weird block layout grid sometimes on the surface, or a few blocks beneath the ground.
I was created the world around January,

I also had these experiments on: Holiday Creator Features, Upcoming Creator Features, Bata APIs, and Update 1.21
The seed is: -5071814561777723473
The coordinates are: -1505 58 -418

Steps to Reproduce: Try these.

1. Create a new world using seed(-5071814561777723473) with 1.21 update and
other experiments turned on.
2. Set gamemode to spectator.
3. Locate the Village at -1505 58 -418
4. Look underneath or on the surface of the village for any patterned blocks.