I’ve got a couple of SSC P4s in my inventory, I don’t remember what I bought them for but they must have been for some project or other that never got started! The SSC P4 used an XR-E die from Cree but Seoul Semiconductor made their own phosphor and packaged the LEDs.
The XR-E does in fact have a centre thermal pad and it’s electrically isolated from the other two.
See the second to last page of this this PDF
In this thread its suggested that it will fit one of the Noctigon boards (MT)