The NRLW could absolutely use all of the popularity boost it can get (ridiculous to pretend couldn't use help in that regard) and she would be the most popular/followed player in the comp by a long way. “More will come and go” really doesn’t apply here because literally no one of her popularity has come nor gone. She's got 60k more followers than the competition itself let alone any individual players.
As I said above I can somewhat understand the logistics argument of the timing (though why does the NRL really care if the Knights have a backup winger in the team for a week or 2 instead?), but who cares if a legend of rugby who’s in theory bringing new eyes to the NRLW is also still involved in promoting rugby? No one who's following her doesn't already know what rugby is, but plenty would be non-NRLW followers who could be introduced through her.
It’s also not like she’d be promoting it on the field or in her Knights/NRLW media appearances obviously. Just seems like the NRL shooting themselves in the foot for some dumb precedent that no one will know or care about.