Usefulness in websocket version 0?

Hello! I’m going through the websocket protocol in autobahn and stumbled across some logic that uses the websocket version 0

See the above attached function. Instead of appending the data directly to the framer buffer it has a prior check to determining if the websocket version is 0. If it is then it appends the data directly to the “message_data” buffer instead of the frame_data buffer.

Is this something internal for testing or does a websocket version 0 exist that needs separate logic?