I think that is bit misleading; this paper specifically did not analyze the effects of ECC at all, all their work is strictly focused on non-ECC systems. All the references to ECC are to other papers. Furthermore, while not "fully adequate", ECC is still quite effective mitigation
> [...] existing hardware countermeasures such as using memory with error-correction codes (ECC-RAM) appear to make Rowhammer attacks harder [...]
> ECC RAM can detect and correct 1-bit errors and, thus, deal with single bit flips caused by the Rowhammer attack. [...] However, uncorrectable multi-bit flips can be exploitable [2, 3, 42] or can result in a denial-of-service attack similar as described in Section IX-A depending on how the operating system responds to the error
Unless the situation has radically changed, my understanding is that ECC changes Rowhammer from a practical attack to more of a theoretical threat. And generally DoS is highly preferable over something like privilege escalation, which is further benefit of ECC.
Consumer-grade ECC can't come soon enough.