I'm coming back to note: die shrinks, density increase, and frequency increases- while keeping costs from going out of control all work together to make rowhammer inevitable. I maintain they knew about it, dismissed it as impractical, tested if it was a concern in normal usage... and were surprised + hobbled by their pants, when a PoC hit the public.

I'm not versed in silicon fabrication to know if theres ameliorations involved past what hit the press near 20 years ago now. But, while deep diving modern DRAM for an idea, its shocking how small a change is needed to corrupt a Bit in DRAM.