4DS - Anything but Charting, page-28454

You are incorrect that 4DS memory is Not non-volatile". For it work within both the DRAM and NAND space (Storage Class Memory) it has to have retention. With Volatile Memory as soon as you remove power to the chip it looses all the data.
With Non- Volatile memory it the data is embedded on the chip until it is overwritten. It holds its state until that cell is addressed again whether it has power or not.
4DS is Non Volatile memory where the retention can be tuned by design for the application to be used, i:e Storage Class memory where if power is removed it will retain the data for the designed amount of time.