When I see that phrase (or similar), as e.g. today in How to Use the free Command on Linux (article with 2020 date):
RAM that isn’t being used for something is wasted RAM
I recall about LPDDR used for mobile devices:
Additional savings come from temperature-compensated refresh (DRAM requires refresh less often at low temperatures), partial array self refresh, and a "deep power down" mode which sacrifices all memory contents.
As Android is based on Linux kernel, does it already supports putting part of memory in "deep power down"? Some kernel parameters to enable managing data in a way to minimize total memory usage?
In total: has Linux kernel abandoned universally applying "RAM that isn’t being used for something is wasted RAM" approach?