On simulator play, anyway. It's recently been discovered that stat drops are calculated a bit differently in the first two gens, and you can see the details here. It seems like it would be a fairly minor detail, but it ends up breaking some speed ties when Curse is involved. The most obvious and common example being -1 Skarmory against Belly Drum Snorlax; whereas both used to be tied at 158 in simulator play, -1 Skarmory clocks in at 157 in reality. It's not huge, mind you, but it's a little extra edge for the fatty, who quite frankly didn't need it.