Wrong assumptions alone don't make a question off-topic or unfocussed. But quite often questions with wrong premises or wrong assumptions come with other weaknesses which justify closage. The first two questions you cited are clearly examples for this.
I cannot speak for the other voters, but I voted to close the first question on your list because the core statement was looking so wrong for me that I thought "that literal question is surely not really what the OP meant". It gave me the impression of being worded in a way it would easily cause wild opinionated guesses of what the OP really had in mind. The OP in between admitted they did not express themselves well and expressed their intention to improve the question - still they did not fix it yet, four days after the closage.
The second one was not critized because of making wrong assumptions, but because of the (probably wrong) impression the OP was going to judge their team members in a code review. When told, the author fixed that (which means your citation of the title in your meta question isn't correct any more, btw.). Me (and others) voted the question up afterwards. Still, a diamond mod closed the question as "too opinonated" (which I can perfectly understand when reading the very different answers the question got).
The third and the fourth one were well received by the community, I don't have the impression they got any close votes for having an incorrect premise.
So in short, a wrong premise or wrong assumption alone is not a valid reason for closing a question - but also not a reason to keep it open. And quite often fixing a wrong premise in a question can help to avoid opinionated discussions.
