Carcharias, you are the one claiming she has an agenda, I don't know what you think it is.
Why didn't she wait for proof? What standard of proof would satisfy you? Sometimes, for any number of reasons, sources ask to remain anonymous. Sometimes there are legal reasons that certain facts are not publishable, perhaps for instance, to do with signed confidentiality agreements. Stories like this are published every day and I would bet my bottom dollar that these claims are not fabricated by Magnay. If they are mistaken and she didn't adequately check the veracity of what she was told then I'll agree with you that this is sloppy journalism, but I'm not going to agree with you just because Zappia denied the allegations in the face of an incredibly meek interview on the NRL's flagship publicity program. Vossy didn't ask a single follow up question ffs.
Magnay reported on information she claims to have been gathering for months about the culture at the Sharks. She pursued Zappia for comment in the course of her investigation and he refused, except for a text message sent to her on Wednesday night that she reported. She claims there is more on this story to come.
To me, all the indications suggest that Magnay is confident in her story.