Nas wasn't fucli
Depends on what stage said British act was on, if it was a dance stage then I would say so. Nas' name might not have been largely placed on the ad, but you're the final act to preform your considered the main event. As you saw from the video many people still stuck around for him after Pharrell left and it was good crowd so for all intents and purposes he pretty much was a headline act.
Heck if you wanna look at it another way, when the set times came out, he had top billing on the stage