I am on a server on 1.17.1, that is also using the original caves and cliffs data pack to generate the world. I made a guardian farm, that for some reason was only producing a few guardians a minute, despite caves being heavily lit up. However once I made the bottom half slabs on top of the farm into full blocks, I got full rates. I then went to another temple, and it is also not producing many guardians. So I think there is a bug that makes it so guardians are not spawning properly with out a full block above them