'Do with' not 'do in'. For example, there could be an ether-tcp that transports data using unused header bytes. Now factually you don't send data 'in' TCP header so TCP-ether might seem better, but actually you can send data 'with' TCP and thus TCP-ether is redundant.
Think of any Ethereum usecase and you can do it with bitcoin.
Voice can be transmitted as packets using IP, but is VOIP an extension of IP or core use of it? Well, I guess we can call it either, because the end result is similar (but the side-effects are not).
Think of any Ethereum usecase and you can do it with bitcoin.