When you sign up for drone license, you hit agree. Recommended has been around for a long time in a FAA Advisory Circular. In full scale aviation when talking to a tower, the tower will ask you to do something, it is not binding until you agree. Then it is expected. It is usually the right thing, but every once in a while you will hear" unable to comply" and then they will try to take your recommendation. The FAA is treating everyone just like full scale. Hit agree and it is binding.
Read it again. It say's "guideline". It is not actually a requirement. The only 400 foot requirement is for fields within 5 miles of an airport.