A page is one way to hold a boundary. Here is another.
Think about how you dress. There is a version of you for a client pitch, a version for the Monday standup, a version for a wedding. Nobody would call these different people. They are the same person on different occasions, and you move between them without instruction.
Notice what changes and what does not. The dials are identical every time: how formal, how much colour, how much structure, how much you are visibly trying. What changes is the range you allow yourself on each one.
That is a different kind of boundary than a written rule. It is not “wear navy.” It is “on this occasion, formality sits somewhere between here and here.”
Now the same thing for a brand. Informing and inspiring are not two brands. They are the same axes with different permitted ranges. Informing wants proportion, evidence, restraint. Inspiring lets the image carry and lets the page breathe. Both are unmistakably you, and neither is a relaxation of the other.
Which is the part a single document cannot do. One document describes one region. But purpose varies, audience varies, the moment varies. So either you write a separate guideline for every combination, which nobody does, or you accept that the written version covers the average case and leaves the rest to judgement.
There is a third option. State the axes once, and state the range per purpose. Then the boundary is not a page any more. It is a set of coordinates that moves when the purpose moves.
And a coordinate can be checked.