Port 9735 for both MAINNET and TESTNET

[Bitcoin]

Port 9735 for both MAINNET and TESTNET

The default port for the Lightning Network is 9735. This is the case not only for nodes on MAINNET, but also for nodes on TESTNET.

Why is that? What's the purpose of this? Wouldn't it make more sense to use different ports for the different networks?

Particularly if you run a MAINNET node and a TESTNET node on the same machine, how would the host know which incoming traffic is intended for which node?

Source: Port 9735 for both MAINNET and TESTNET