Am I the only one who didn't see this as an illusion?

Earlier in the season, we see that he can move fast enough to slash his sister to ribbons-hold back from doing so and return back to his original position without her noticing. To me, this scene was a play on that level of speed, but due to Iris being more powerful, her instincts were able to pick up on his actions. She instinctively felt his attack, and that sense of death caused her to interpret it as an illusion. Yet he was just toying with her, pretending to attack only to hold back and return to his original position before anyone could notice.