In case someone is wondering, ECC DRAM does not prevent rowhammer attack.
If you flip only one bit, that will at least increase a correctable error count. It you flip only two bits, most OSes will panic, although sophisticated OSes can kill only the process which had that address mapped, or take that address out of the mapping and kill the process on access, etc. It's only if you flip three bits that it might be undetected.
From what I've seen the probability of flipping one or two bits is much higher than three or more, so ECC is useful to probabalistically turn a security bypass into a denial of service.
There's also a potential performance tradeoff (no idea if GCP is using this) of running some single channel DIMMs for isolating VMs from the kernel and kvm userspace.
Reference: https://www.google.com/amp/s/cloudblog.withgoogle.com/produc...
Which is to say, it basically prevents rowhammer in a practical sense. You can flip the bits, but you don't have the level of control needed to flip the right bits.
But dropping the analogies entirely and stating explicitly is a lot better. ECC makes rowhammer less likely to succeed and slower to exploit.