On the one hand, yes, on the other hand, no. I want to speak strongly against adding a crappy close reason, but would support a good close reason. I am making an analogy to a different SE site which has crappy but well-intentioned closure reasons, which I believe are misapplied in vast numbers of cases.
First, drawing analogies to physics and math is wrong: law is not physics or math. Second, the rationale behind such a ban is not that the question comes from a textbook, it is that it is a "do my homework / exam" request. I also dislike some of the questions that you're asking about, but I am not persuaded that these are "do my homework" questions. In fact, I think those questions (most of the time) are unanswerable opinion questions. The essence of the majority of these questions (or at least the ones that stick out in my mind as bad) is asking why a textbook author say something one way and not another. Questions about pedagogical strategy is totally off topic for Law SE, and probably unanswerable in the vast majority of cases.
We have also had related question about why a particular justice said X in their written opinion. Questions about phrasing are off topic, questions about legal principles are on topic: there is my proposed rule (first draft).
I believe that just saying "textbook questions are banned" is a bad idea, but first characterizing the problematic nature of such question is a good idea. As a first pass, you might object "You didn't even try to figure this out". The problem is that for most questions, they evidently didn't try to figure it out. There must be a thousand question here asking if it's legal to violate copyright law in such-and-such circumstance where anybody that knows the first thing about copyright law would know. I suspect that at least half of the questions we get are non-challenging.
The typical "textbook" question is actually somewhat challenging. As a start, I urge you to identify the specific harm done by such questions.