OTOH, a rowhammer attack on ECC memory will likely flip 1 bit before it flips 2, making attacks theoretically detectable. Without ECC, there's no clear way to detect an attack.
ECC memory controller performs memory scrubbing periodically, in the background, during which it checks parity and corrects any bitflips. Otherwise ECC would not work nearly as well as it does.
AFAIK, row refresh is done within each memory chip, while the ECC bits are normally on a separate chip (for instance, where a non-ECC module has 8 chips, an ECC modules has 9 chips), so ECC scrubbing has to be done in the memory controller.