Hope you change this in your guide because you really are misguided in this advice. Thanks for your note, Tipmore. It provided a reason to 'talk' with our Swiss friends. Our friends are professionals or business owners. Tipping custom is a bit, only a bit, regional in Switzerland.
Tips tend to be higher, on average, where there are tourists.
Higher in the large cities. Smaller, or non-existent, in smaller towns and villages. One friend tends bar part time and expects basically no tips, though they sometimes put out a dish with some change in it and collect the occasional 20 rappen. I don't know where you wait tables, Tipmore, or the nationality of those you work with. That might influence custom to some degree, and surely might influence expectation, whether realistically or not.