You are confusing the device driver layers and the IP layers of the stack.
At the IP layer, 127.0.0.1 is just another IP address and treated the same.
At the driver layer, packets sent via the loopback interface are "simply and immediately passed back up the network software stack" as opposed to being sent to a network card.
This concept is not OS specific; various OSes use the same concept.
You have confusion between localhost (127.0.0.1) and loopback interfaces. Yes, you are confused between the network stack layers.
In computer networks, the lower layers than the network layer is the data link layer and the physical layer. Where is the device driver layer in computer networks?
It claims the concept is not OS specific, so I try my luck here. So did I in the question (Does a loop back IP address not need to be assigned to a network interface, in order to communicate with?) which I want to know the most. Some users on both sites (Unix and Network Engineering) claimed the same questions belong to the other side, saddening me.