From what I remember the 1200 and 1000 revolt x are built by Seasonic but I can't say if the adapter is keyed the same as their focus platinum units. You should probably contact either Phanteks or Seasonic to make sure. Even if the PSU side looks the same, it may not be wired the same.I have 1000W version of this PSU and just bought a 4090, but I also bought a Seasonic 12vhpwr cable.
From what I've read, phanteks is basically a rebranded Seasonic. If so would the adapater work?