Intel's current generation CPUs have the same dual-channel LPDDR4X memory that Apple uses. Memory is not "on the same die" for either company because you don't make DRAM on the same process where you make CPUs.
Regardless, the big win was giving unified access to that memory using a memory fabric. That lets the GPU (for instance) access graphics assets with no copying - it just uses them in place.
AMD can absolutely do the same thing, if it desires. Intel can too, but it has a hill to climb WRT GPU performance.
Apple's AI chiplet is another matter...