Because it’s GDDR memory, not DDR. They’re two different standards that aren’t interchangeable.
https://www.technipages.com/whats-the-difference-between-ddr-and-gddr-memory/
TL;DR it’s like the difference between a GPU and a CPU. Similar acronyms, different function.
My brother had one of the original Moto X phones which had this neat gesture where you waved over the screen and it turned on to show you your notifications. I think it was a basic proximity sensor thing, but it was super useful when the phone was on the table.
Can’t believe I haven’t seen it since.