R53 MCS ..I'm watching mod minis video on replacing a head gasket and I see he removed the rocker arms and cam shaft . I don't see why that's necessary. Am I wrong ?

 

If I remember correctly you do not have to. However you still need to lock the cam gear in place if you are going to keep it in. It not to big of a deal to remove the cam. It a good opportunity to examine each lobe for any premature ware.