caranthir:
I agree that if we have the ladder, then P4 is locally better. Interestingly, on empty board, if we don't have the ladder, Katago prefers Q6 over Q2 for potentially more complicated stuff (while P4 is obviously unplayable). I modified the problem to allow P4, and stated that the task is to connect. -- Many problems in this collection must in general be taken with a grain of salt. For a beginner they teach basic intuition totally fine, but more experienced players can remember that in many cases there are additional options depending on whole boeard distribution and even playstyle. Unfortunately, making the problems more exact would demand them be made either within whole board context, or unpractically heavy on variations, and I don't think that would serve the purpose of this collection.