I don't see any problem with allowing these kinds of questions and letting people answer them, provided the question and answer(s) are written (or edited) to the standard expected. Remember that it's been stated before by Jeff and others running SE that a certain level of duplication is good - we often want to see a few different "flavours" of the same question to help people searching for answers to similar questions they might have.
I would also suggest that as one of the problems we have on this site is low engagement and volume of questions, this could be helped by allowing these technically duplicate questions to be answered specifically, as this would encourage the question asker to post more (hopefully more interesting and useful) questions, rather than giving them a negative experience on what is often their first contact with Poker.SE.
If we are going to close questions like this as duplicates (or define them as off-topic), we need a standard place to reference the question asker to, whether this be another question on Poker itself, or here on meta. That place to which we direct people asking "who won this hand" type questions needs to provide that person with sufficient information to be able to answer their own question.
Initially, perhaps this is just a Wikipedia page or something similar which explains how poker hands are compared at showdown, then if users are still unclear as to who should have won the hand, they can ask a more specific question, referencing the material they were directed to, all of which will help satisfy the "shows some research effort" criteria for good questions.
Over time, perhaps we can build a CW answer to a question which deals comprehensively and clearly with all necessary variables that affect who wins a hand, then we can close questions as dupes of that, or flag for closure as low quality (i.e. they haven't read the resource which is already available).