From what seemed to be an easy victory for the Saiyans, Black turned it around rendered them completely helpless before him. Each clone are more than capable of causing real damage to them, and Goku and Vegeta were not able to even escape them. They could easily have if Black ordered them to. The clones didn't destroy them, or even knock them out.
That is infinitely better than Vegeta destroying the Room of Spirit and Time after channeling the depths of his strength. His raw power improved to the point that he tore through time dimensions (something that only a Time Ring could do) with a flick of his wrist. He used clones, doesn't mean his own raw power improved. I'd take that quote with a grain of salt if you have to limit the extent of Goku's power to prove that quote right. Are likely talking about Goku without Kaioken, since they mention his strength being on par with Frieza, which only SSB Goku is.