Documentation of architecture and information flow should ideally be written before the code (as specifications, plans, RFCs, etc). They should be required to be merged into the repo along with the code, just like test, and just like method-level and class-level documentation. Documentation (and testing) should not be an afterthought.
Documentation for end-users and wiki-owners will generally not live in the same repo as the code, since it's less "bound" to the code, but it should, ideally, also be written *before* the code, as user stories, UI designs, etc. Turning the plan into proper documentation may happen after the fact, but then it's the responsibility of the team who deployed the feature to make it happen.
In my mind though, the architecture principles don't really apply to documentation for end-users and wiki-owners. Combined with the lead sentence of the section, the principles reads: "To maintain a code base that can be modified with confidence and readily understood, comprehensive documentation MUST be maintained along with the code." I think it's pretty clear that this refers to documentation of the code. Do you think this should be made more explicite?