Had to check, but mine has the hole too, you will find when you ride longer distances, the oil will seep out the valve lifter cable hole at the back, this was so bad, that I soldered the supply pipe half shut, seems to be OK now.
Also advisable is to replace the paper gasket for the valve cover, with one made from graphite material, as the paper burns away after a while.
Cheers,
Lex