Good question. But I don't find 25% getting it wrong at all surprising.

I imagine what most of those 91 learnt was to be a bit more careful in their reading: a lot of people will have seen at a glance that the view is an updatable view of a single table and that the where clause of the update query unambiguously defines which underlying data is to be updated, and gone for "yes" because the question is about updating through a view, then kicked themselves because they had carelessly failed to check that the new value was legal for the column. I've seen so much of that sought of carelessness in practice that I reckon that's a very important lesson for DBAs and Developers to learn (especially those doing 2nd or 3rd line support, who often have quite extensive power to modify production systems, and those doing QA, who have the power to let all sorts of rubbish get into production if they are careless). So keep up the good work with more questions like this.

But the choice of reference was not really a good one; that BoL page doesn't tell you anything about this QotD except to go look at a different BoL page.