It likely depends if there is any DL metal involved. When I purchase tickets on DL.COM and add my Worldperks number to it, any NW metal segments show up on nwa.com with a separate NW itin locator. However, if it's all DL metal, nothing will show on nwa.com.
I have an award with DL and NW segments - if I change from SM to WP, all five flights disappear from .bomb. No matter what, none show up on NW, although I can look up the flights with the locator (e.g. to assign nice WBC seats on the 330).