Sorry, Eliot, I didn't understand it either, particularly about lateness.
The point of the paragraph is to declare PM to be something that
should be considered at architecture time, i.e. early in the design
process, when the fundamentals are worked out. (Personally I would
prefer to make it a general statement about "privacy", not just PM,
but I'm glad to get whatever I can.) The statement is not that
architectural issues need to be considered early (that just begs the
question), but rather that PM needs to be considered an architectural
issue.
Scott