Hi,
Based on your description, it doesn't appear to be an issue with Distributed Rendering (DR) but rather an expected behavior of your network adapter. During DR, the network connection is being used, and the network adapter prevents the system from entering sleep mode. Additionally, there may be other hardware components that could prevent your computer from going into sleep mode, which you can check by going to the Device Manager and reviewing the power management settings for each device. In the case of DR, it's especially important to check your network adapter's power management settings.
I hope this helps.