No, definitely not an "always" rule. It says that in the stickies because when folks are new, they are often uncomfortable/inconsistent about testing, and there isn't a lot of data to know how a cat will respond. There are also a lot of people who join, read the stickies, and then go away and do it on their own, without every posting for help. For those reasons, the stickies are the most conservative approach to dosing - they are designed to keep kitties safe when their caregiver may not have the skill or wisdom to use a more complex and nuanced approach.
Once the cat and the human are used to testing, and can be sure of being able to get a test when needed, and understand how important that data is, and how to use the data appropriately -- then it's not only safe, but necessary to dose below 200. You cant' usually get a cat into remission without breaking that rule.