I may be wrong, but I'm pretty sure nobody except the Sect Master and one of the Guardian elders know about Arthur's identity as prince and that he has a mask on. Was the revelation of his identity and taking off his mask skipped?
Luke knew from the start, Balor after he became Arthur's disciple, while Sun Wukong was the last to know but he didn't even care. But I skipped detailing those parts. Only Luke's own was clear from the start.