First time I heard this claim although some googling shows that it has some support. I wonder if it continues to be immune if the attacker flash freezes the RAM. It seems the reason given for its immunity is because it clears its state in only a few seconds after power is cut, not giving an attacker enough time to transfer the RAM in a forensics laptop or even to reboot the system the RAM is in and load a live light weight forensics OS. However if they gain access to the computer and it is booted up, I imagine they can still freeze the RAM to dramatically extend the amount of time they have to put it into a forensics laptop or reboot the targeted system into a forensics OS. Also I cannot find any actual studies or experts talking about DDR3 RAM and cold boot attacks, only random people on the internet making claims about it. Thus, I am skeptical about the truth of this until someone shows me a study or a recognized expert saying something on the matter.