"Unified memory" doesn't really imply anything about the memory being located on-package, just that it's a shared pool that the CPU, GPU, etc. all have fast access to.

Also, DRAM is never on-die. On-package, yes, for Apple's SoCs and various other products throughout the industry, but DRAM manufacturing happens in entirely different fabs than those used for logic chips.

System memory DRAM never is, but sometimes DRAM is technically included on CPU dies as a cache

https://en.wikipedia.org/wiki/EDRAM

It's mostly an IBM thing. In the consumer space, it's been in game consoles with IBM-fabbed chips. Intel's use of eDRAM was on a separate die (there was a lot that was odd about those parts).