I don't think that's even true with my m3 mbp16. I haven't tweaked with the power settings but I'm pretty sure it is in a connected sleep state when I close the lid; at least when I'm hotspotting my phone will register it as a connected device.
This can be enabled or disabled under the System Settings > Battery > Options > Wake for network access (Always / Power adapter / Never). Or possibly the phone registers it as connected for a while after it sends its last packet?
IIRC, Macs also do tricky networking things to make it faster to come back online from sleep. I'd be curious if the computer is actually sending packets vs. just keeping the address configured and waiting.
