Whatever the difference is, it can’t be big. For example, the M1 Air had H9HCNNNCRMMVGR-NEH chips in the iFixit teardown. That exact product doesn’t appear to exist at
https://product.skhynix.com/products/dram/lpddr/lpddr4x_4.go. Either it doesn’t any more, or it was never for sale to third parties. Perhaps Apple bought the entire production run. Perhaps there’s something unusual about the configuration that Apple requested. Perhaps the configuration is normal, but Apple requested the real specs be obscured.
Here’s a deciphering of the markings. That post also lists two very similar chips that can be purchased.
If the deciphering is to be believed, the first only differs in its die generation, package option, and operating temperature. The second in its power supply, die generation, and package option.