Newer laptops with Intel cpu (not sure about AMD) don’t have a real sleep mode anymore. Instead, they have a mode where, besides the ram, the cpu and the network device are also kept alive for communication.
In theory, this means that when you wake up your device all of your apps and stuff will already be updated with the latest information from the web with little battery loss. In practice, it just overheats your laptop while in your backpack and kills the battery.
The ping you see while it is “sleeping” might be from this.
I think the worst part is not that they added it, but that they removed regular S3.