Here are the instructions to make WSA receives such traffic.
1. Ensure WCCP will redirect 5443 traffic from network device to WSA.
2. Ensure port 5443 is added into the "Port numbers" settings of WSA WCCP configurations.
3. Add port 5443 to WSA HTTPs Ports to Proxy via WSA GUI>Security Services>HTTPs Proxy.
4. Also ensure port 5443 is added into Access Policy>Protocols and User Agents>HTTP CONNECT Ports.
Hope it helps.