I think the reviewer is mostly right though. The M1 uses unified memory where the CPU, GPU, the neural processor, and other components can access the same data without copying it.

"All of the technologies in the SoC can access the same data without copying it between multiple pools of memory. This dramatically improves performance and power efficiency. Video apps are snappier. Games are richer and more detailed. Image processing is lightning fast. And your entire system is more responsive."

Of course if you need 12 GB of data in memory than sharing 8 GB won't be enough but for most current uses of 16 GB its possible that 8 GB could feel as responsive between the shared memory and the faster access speeds (due to faster components and smaller distances)