It's called staying on topic, which is the intent of the article. 

If the author had drifted to other facets of the tax reform for the wealthy, she could have noted the lowest earners' taxes would increase from 10 percent to 12 percent, but that would be an entirely different topic. 

Bottom line: Wyden is correct. The GOP tax "reform" gives huge tax cuts to people likeTrump, leaving nothing of value for the middle class.