Never mind that Apple AFAWK doesn't use either DDR4 or DDR5 RAM in its M1s. It just uses Unified Memory DRAM:
View attachment 1904227
As explained in
With M1 Macs, memory just isn’t what it used to be you really can't compare the way memory was (and likely will continue to be) used on Intel systems.
"The M1 processor’s memory is a single pool that’s accessible by any portion of the processor. If the system needs more memory for graphics, it can allocate that. If it needs more memory for the Neural Engine, likewise. Even better, because all the aspects of the processor can access all of the system memory, there’s no performance hit when the graphics cores need to access something that was previously being accessed by a processor core.
On other systems, the data has to be copied from one portion of memory to another—but on the M1, it’s just instantly accessible."
That part is key and why Intel machines needed eGPUs and more RAM - the CPU had to play chicken/hen-fox with video and system memory and the extra ram was the "boat" so to speak. The M1 eliminates all that.