“I disagree with this decision. The riff used (similar between songs, but not the same) is widely circulated in hip-hop/rap crossover music, including dubstep.”
My son is a producer/writer/engineer in several genres, including those you mentioned, and he is on the same page as you. He played me the riff in question, and I agree as well - I wouldn’t have voted for a plagiarism verdict were I on the jury.