To clarify something first: There are some questions which I believe are contained in what FuzzyChef terms "restaurant practices", and they are already in scope. These are the cases in which an asker wants to emulate restaurants, and asks what restaurant-level techniques exist for cooking something specific. They even have a tag, [restaurant-mimicry]. Also, I don't think that we want to open ourselves to pure rants (which typically get formulated as "why do they do this" questions, which FuzzyChef also argues against). So the remaining category here seems to be questions about the prevalence of restaurant practices, basically "how commonly is X done in restaurants" (or its subtype, "is X done in restaurants [at all]").
At first glance, having these questions sounds reasonable. People who work at restaurants should know what is done in restaurants.
Looking closer, people who work in a restaurant know really well how things are done in their restaurant. Or maybe 4-5 restaurants, mostly in a single geographic area. So we will have questions about the general prevalence of a practice, answered with a collection of single data points (even if answerers present them as relating to all restaurants in general) - or in other words, a poll.
In the earliest days of the network, poll questions were in scope. Pretty soon, people realized that they do not work well, together with big-list questions (indeed, some older Meta posts don't distinguish the two). That is why they were forbidden, out of hands-on experience with them. They just don't mesh well with our system design. There was quite a long period of time in which they even had their own close reason, until the company decided to revamp the wording of reasons, and so they were by default folded into "opinion-based" as the closest remaining heading.
Also, there is another requirement for questions that was, at the beginning, common for the whole network, and is still written down in our own Help center: We only take
practical, answerable questions based on actual problems that you face
and we don't take subjective questions, especially when
your answer is provided along with the question, and you expect more answers: “I use ______ for ______, what do you use?”
there is no actual problem to be solved: “I’m curious if other people feel like I do.”
I would argue that questions of the type "do restaurants actually do X" fail these requirements. They seem to be powered by sheer curiosity. Also, the answers will indeed be of the type "My restaurant does X [in way ABC]", sometimes insidiously hidden in a (most probably mistaken) generalization, "restaurants do X {in way ABC] all the time". So this is a second reason why these question go against the basic design of the network.
For me, the second argument wouldn't be a dealbreaker. A lot has changed since Jeff (the network founder) argued passionately against "frivolous" questions which would make the sites less serious and professional. We even have sites which do nothing but types of questions he disapproved of early on.
However, the first problem - the polling part - is a very serious no-go for me. It is not just part of a now-gone-boss's strategy; they were tried, and found to not work well.
Also, if we drop the parameter "about restaurants: yes/no", which until now has been orthogonal to site scope rules, these questions fit nicely into existing categories. They are poll questions; they are questions-without-practical-problem; and they are questions-about-human-behavior. From this point of view, allowing this subset of questions will create an odd-one-out exception.
Again, this is not to be understood as an argumentation against all questions which are somehow related to restaurants; these questions can be further treated according to existing rules, with closing the closable ones and keeping the in-scope ones. In this case, I personally find the status quo reasonable.