The timing isnt lost if those 3 bolts are loose, you have pinned the cam sprocket so it cannot move.
I think the idea is to aid belt alignment and help get the slack out using the tensioner. Some cars ask you to set the sprocket to the middle of the slots and others fully clockwise, i supose it depends where the tensioner is.
Sometimes when you rotate the engine twice after completion to check alignment then the cam timing may be slightly out, if so you can then pin the crank sprocket at tdc and slacken those 3 bolts to get the cam back in line and get the timing pin back in.