Missing information on Future API documentation

I believe the documentation for USD-M and COIN-M futures is missing the trade endpoint for the websocket. Testing locally and I’m able to access by subscribing the same way as the SPOT API but using the symbols obtained through the respective API. Can I assume that what I’m receiving is correct?

it’s not listed in the API document, so it’s official support, please be advised that it can be changed without notice.

Did you mean it’s unofficial support?
I understand that if it’s unofficial it could be changed without notice, is there a plan for turning it official or will it never be supported?