See also the timeline of those PCM, based on chalcogenide glass, which were invented in the 60ies by Stanford_R._Ovshinsky. He always insisted that it's better than DRAM. Finally we are getting there.

https://en.wikipedia.org/wiki/Phase-change_memory#Timeline

Theoretically it should be 1000x more durable than flash, and also 1000x faster, but they are not there yet. But it looks like they solved the packing problem. And Micron insists that it is chalcogenide based, but not "phase-change memory", the one they started in 2012 and took back in 2014.