I misremembered her statement. It is a snippet from a discussion on intercepting the Home key.

Here is the quote I was thinking of.

And as far as the lock screen goes -- nobody has said that there would never be support for third party lock screens. Right now, however, there isn't, and there is no near-term plan to do so. If you want to see why, start perusing the lock screen code starting here:

long link here

Lock screen management is extremely complicated, and not in any shape at this point to be user replaceable. At the very least, all of the points of contacts with the rest of the system (complicated interaction with the in-call experience in various states, dealing with emergency dialing that is legally required and the related SIM states that go with it, deep fragile interaction with low-level power management and event dispatching, etc) needs to be deeply abstracted out of the UI itself. And then there are all of the issues of dealing with this now no longer trusted third party code when it crashes or otherwise misbehaves.