It's part of the choreo. Chen is supposed to do it to Sehun as well but he kind of stopped doing it (or at least it's never really shown since its during Chanyeol's lines) it's easier to see in the leaked dance practice. I think they're just supposed to look like they're pushing them to the front.
저때 저기에 있었는데 예상 인원보다 사람이 진짜 많이 와가지구 거의 의자에 앉아있는게 아니라 다 서서 보고 의자에 올라가서 보고 이런 무개념들이 많아서 몬스터 무대 하다가 위험할 것 같아서 멈추고 무대 한번더 다시 한거에요ㅜㅜ멤버들이 계속 주의주고 우리 조심히 보는게 어떨까요 이랬는데도 중간에 막 올라가고 이런사람들 있어서 기분도 나쁘고 지방촬영이라 피곤했을 것 같아요ㅠㅜㅜ
attention all baekhyun stans, your bias had finally officially revealed his abs at an exo concert like a night ago. You can search for it on RU-vid. just type baekhyun abs and you will see a bunch a videos. warning though; you may die from extreme hotness.
