Scalability with Ethernet is about:
a) the capability to add more nodes (devices, computer, or whatever) where and when required, while maintaining an integrated management view
b) being able to increase the bandwidth or redundancy of connections
c) use the same network for multiple systems, while maintaining the bandwidth requirements for each.
These facilities allow a bedroom hobbyist to expand to a small studio, to a multi-room suite, to a major player, without having to start over at any expansion stage. Equipment doesn’t have to be abandoned, but just moves to the periphery, as bigger Ethernet devices take over communication management.
Conceptually, the system does not change, no matter what size it is, or becomes.