These anti-quads are so anti-everything that their antipathy needs to be spread out across four different cells to avoid overloading a digit. They might only list the digits they’re most against, but they don’t want any other digits doubling up, either.
The last puzzle I published with “anti-quadruples” fully filled each anti-quad circle, providing maximum information about what wasn’t there. This time, a few digits seem to be missing, and most of these circles eliminate very few candidates each.
Continued research into the issue of Anti-Quadruples has exposed why we had not seen them before. They are best detected not by observing them directly, but by observing what isn’t there.
Testing hypothesis: For every constraint, there is an equal and opposite anti-constraint. Research into quadruples has turned up anti-quadruples in far greater quantities than theory suggested. Further research will be required.