It's a board space and cost saving measure but it does not change performance. The tooling is also expensive and Intel have their own internal mature packaging processes.
The drams on an apple chip are still bog standard lpddr. Most benchmarks find the actual memory middle of the road at best.
Critically they aren't magically on the die or any more inside the package than most other high end mobile chips.
ram is ordinary POP, you got lied to by Apple marketing. If you acted on this marketing and spend money then re-programming will be very difficult with brain actively fighting on every step to prevent cognitive dissonance.
The drams on an apple chip are still bog standard lpddr. Most benchmarks find the actual memory middle of the road at best.
Critically they aren't magically on the die or any more inside the package than most other high end mobile chips.