If I get some time over the next week or so I’ll have a look at implementing it! There is also a small bug that causes errors in the console if you delete an object, so this will be a good excuse to combine both for a more significant update
The reason Anti-tile doesn’t work within groups is because it only checks the material node tree, not the node trees of groups (as this could be recursive). This means even though you are viewing a node group, Anti-tile only sees 1 node group selected on the top layer.
This should be relatively easy to implement (theoretically), but for now you will need to ungroup(alt+g), apply Anti-tile and then regroup (ctrl+g).