In these instances, should the question be closed as a duplicate or do we want to consider it a separate question since it originates from a different book?
We should not close questions about different texts as duplicates. Even if the story is the same word for word, the narrative context is always different between the synoptics. Even in the case of an identical question quoting identical text, the best answers will take account of the surrounding narrative.
For example in this particular case, the Mark version is part of a deliberate narrative unfolding of conflict between Jesus and the religious authorities. That can have a bearing on how the Mark question is answered in that an answerer may wish to consider the other questions Jesus directs at those opponents as their conflict ramps up: "Can the wedding guests fast while the bridegroom is with them", "Have you never read what David did…" etc
On a site that accepts a variety of hermeneutical approaches I think we should err on the side of caution in these edge-cases. Some hermeneutics are concerned with 'trying to get at the story behind the gospels' (to a degree), but others are more focussed on the narrative message itself, and interpretation is more heavily dependant on narrative context.