I don’t think it’s un-newsworthy. I’m just disputing your claim that journalistic ethics require running it. Both running it and declining to run it are ethically acceptable editorial decisions.
The tacit premise here is that one already knows what the story is and can decide beforehand what information is ‘partial’ and what tells the ‘whole story’.
Absolutely not. The whole story is whatever all the tax returns say. One year could give an accurate portrayal of the whole story, or it could give a misleading portrayal. Both are possible, but there’s no way to know without all the information.