Nope. It only requires being able to read neighboring cells. It would make a privilege escalation attack harder but not impossible. DoS attacks would still be relatively easy.
They are saying that privilege escalation is harder because it's really challenging to target specific bits to flip, whereas flipping random bits will eventually lead to a crash of some kind causing the service to fail which is effectively a DoS
Rowhammer is a memory corruption technique, so if you corrupt the right memory of a process in the right way then you can crash it; same for a kernel or hypervisor.
