Now I could be totally wrong here, but this is what I saw on the Tech News Today (TNT) video podcast.
Apple won a court case concerning a patent they have for the lock screen gesture/swipe action. Basically, they have a patent on the gesture for the lock screen where you start at a specific point "A" and swipe to another specific point "B"! So any other manufacturer or OS cannot have a gesture to unlock the screen where your finger has to Start at a specific point on the screen, and then End at another constant point on the screen, such as the way the iPhone unlocks.
That is why you now have to start (or place) your finger ANYWHERE on the screen, and drag or swipe to any arbitrary area on the screen to unlock it. There can't be any point 'A' to point 'B' gesture or swipe because it violates Apple's patent.
Notice that AFAIK it has only been the Manufacturer's Skins or UI/UX's that have implemented these gestures...e.g. Samsung Touchwiz, HTC Sense, etc.
I'm not sure, but I think that Apple's case was only against Samsung and "Touchwiz", so Google & its pure Android & ICS as well as HTC may be safe from this (for the time being)! In fact, I think this is the reason for the new lock screen gestures, and Face Unlock, in ICS!
Check out Tech News Today Video Podcast #358 starting at 22:50, or search on www.9to5mac.com
So just be aware that if you download any upcoming Stock or OTA manufacturer UX, Gingerbread, or even Froyo updates, you may lose your precious lockscreen shortcut gestures!!!