No, not a mistake. That game apparently uses same format. The “ffsnt.exe” in the files there understands this format, and generates a DDS, although like I said, it doesn’t work properly with DOA6 textures. Maybe the bms script works better.
Original URL: https://www.loverslab.com/topic/117795-dead-or-alive-6-modding-thread-and-discussion/?do=findComment&comment=2545647