My understanding is that all these have in common with RAM is sharing the DIMM connector. There are a number of technologies that use DIMM connectors that are not RAM, for example, the Raspberry Pi Compute Module[0] uses a SO-DIMM connector to save space and money by not having to break out IO nor provide any sort of connectors.
[0] https://www.raspberrypi.org/products/compute-module-3/