At a high level: Intel releases Intel® SDE so that developers can gain familiarity with our upcoming instruction set extensions. Intel SDE can help ensure software is ready to take advantage of the opportunities created by these new instructions in our processors. We hope that developers will explore the new instructions using the currently available compilers and assemblers.
Those examples are a little before my time. :-) But I'm guessing they are a little different. Intel SDE is for running user-level applications with new instructions on top of an existing operating system. Intel SDE does not run the operating system. Intel SDE simulates the additional register state needed so the underlying operating system need not be changed/ported to support context switching the new state. Intel SDE comes with runtime overhead, but many have used it successfully for various things.