Parallel access to memory with multiple DDR4 chips
Unlikely. 

The spec for that shows 64bit wide chunk DDR4. Each of those four chips will be 16bit wide, and all four wired in parallel gives 64bit.

In all likelihood (you can check with schematics), each of the four DDR4 chips will share the same physical address lines, thus preventing using them individually.



From the specifications on the page you link to:


  Memory
  
  2GB DDR4 component memory (four [256 Mb x 16] devices) at 1200MHz / 2400Mbpsps


Note the "four [256 Mb x 16]" - four 16bit devices. Then from the diagram it shows 64bit DDR4. Thus they must be wired in parallel to get the full data width.