The stuff is written down. Just not in the regs
The difference lies in the way the regs are drafted.
If they are prescriptive, they will detail how you are to blow your nose .. a paternalistic approach to life such as we had in Australia years ago
If outcome based rather they will say that you are required to blow your nose ... suggestions as to how you might do that are found elsewhere, typically the ACs. The onus is on the end user folk to achieve the intent of the regulatory requirement.