I don't think it's a big deal and so far this season Ange has shown a willingness to start with different options in midfield even if not so much in game. I think the mistake he has made is thinking once he had the Maddison and Kulu partnership working that, that was now going to be his go to and it can be to an extent but variety is the spice of life and sometimes a different option is going to be the better option.
The promising thing at least from my perspective is he made the change when the game was drawn. He could have felt confident that having gotten back into he match the starting 11 would be good enough to seize the points but he didn't take that risk. He was proactive and made the change before any of us really felt it was necessary. That's what I want to see, bold active decision making, anticipating and reacting to what is happening. It was a great move and paid off handsomely, but it doesn't now make me think that Maddison has to be relegated to the bench. Maybe he doesn't start the next match, maybe he does but it gives me more confidence that Ange is going weigh up his expectations better and if it's not going exactly to plan, change it up to give the team a better chance at righting things.