What cracks me up about it is ...
that you say "it does not really show teachers the HOW of using portfolios/assessment." Let me put in as straightforward language as possible: Students, who have to write using a portfolio, know that if they write poorly on purpose from the start that they will do extremely well in the end because the portfolio is based (seems to me) on improvement and reflection. The students we have in college, though usually not geniuses, are smart enough to know how to play that game especially if they have "played" before.
This leads me to believe that you may be very right in your assumption of a target audience of WPA's. Also, I realize that as teachers and administrators we must depend on the honesty and full participation of students, but should we be realistic or pretend as if that really does not happen....