With the update to 5.1 we've updated the guide to reflect the changes that were made.
We also improved the guide as it contained some minor errors we had not noticed.
Android engineer said the following in another post regarding the Interruptions system.
There will probably be more info added. 5.1 already makes this clearer than in the initial release and things like, "until next alarm" reflect the ongoing refinement.
A big part of this is that a great many people use alarms for recurring reminders, not for waking up. Things like pills that need to be taken within an hour or so of the same time every day, or a weekly reminder to put the trash out. Then life happens; even though you've accounted for the thing it reminds you to do in advance you go to a theater, a funeral, a special session for a class or an important meeting where it's really important that your phone not suddenly start making loud noises. If it does it can have the same level of social consequences as oversleeping.
Hopefully you will enjoy this guide and give us feedback.