Isn't it just the plastic shroud that covers the gears and goes all the way down to the bottom of the block. It's not part of the valve cover. They just cut the top piece of that shroud off. I think it's for looks only and if you ask me it is stupid sense it is there to protect the gears/belt from shit, dirt, etc. I wouldn't recommend it.

PS: I may be wrong, it's been a long time since I've studied a Honda motor, but this is what I think.