That's not exactly true, they can be "unlocked" but not many people have tested and verified that the unlocked memory is stable and/or useful.
But the cards themselves are extremely limited in function, necessitating either board level work to reconnect the electrically disconnected traces or transplanting the hardware to a new board. It's anything but plug and play.
These GPUs physically have 64GB RAM but locked to 8GB RAM. You can unlock all 64GB RAM with a patched driver.
They used to cost $200-250 but now cost $700+.