Comment by Jach

Smart wife. My take on the whole thing is that it's not wise to reason from non-technical metaphors around packages or lawn mowing when the reality is electronic systems. I don't know if it's any wiser but what I like to do is work my way up from the basics. What does delivery mean? Start with two wires, one for signal and one for common ground. (Or just one wire, and pretend you can use earth-return reliably.) If that isn't enough to resolve what terms should mean, consider them with differential signaling. If that still isn't enough to get it, consider them with relay nodes. If at some point "delivery" has changed definitions to suddenly forbid something that previously wasn't forbidden, maybe you've made a mistake.