Seeing his back is about to come into contact with the ground, those wings disappear just in time. He figures landing on those would hurt a lot more then just his back.

He yelps as hits the ground then a slow and sinister smirk spreads across his features. Wei Wuxian has many dirty tricks up his sleeve and once they are like this it is very akin to a previous tumble session they had.

So he wraps his legs around Lan Wangji's waist to lock him there as he looks up at him.