The HC-SWTGW218AS is listed only with the SWTG018AS-A V2.0 board, but it
also ships with SWTG118AS-V2.1, the board of the XikeStor SKS3200-8E1X.
That version runs MACHINE=SWTGW218AS: three such switches were flashed
through the OEM web upgrade and work.
Note in the device page that the model name alone does not tell which
firmware to build.