Microsoft appears to be deprecating sleep in favor of Modern Standby, in which the machine draws enough juice to download and install updates. You know, because Windows is a service, and your contract with the network when you get the show is you're going to install the updates. Modern Standby is a low-power variant of S0, the normal "awake", "computer is on" state.

Because what a PC is is defined largely by the needs of Windows, many systems shipping today do not support the deeper power states (S1-S3) at all, just Modern Standby.