AFAIK, websockets doesn't do authentication? And the encryption it does is minimal, optional xor with a key disclosed in the handshake. It does do framing.
It's not super common, but if all your messages have a 16-bit length, you can just use TLS framing. I would argue that TLS framing is ineffecient (multiple length terms), but using it by itself is better than adding a redundant framing layer.
But IMHO, there is significant benefit from removing a layer where it'd unneeded.