Novice question: If they built something other than classic dram modules with the wafers maybe they could achieve faster bus speeds? How does Apple do it?
Apple uses off the shelf LPDDR modules. They have nothing whatsoever special about them.
Apple gets high bandwidth out of these modules not with high bus speeds, but with a very, very wide bus. This is expensive on the SoC side (requires a large die, which is why others don't necessarily do this), but allows for commodity memory modules.
One of the key points of HBM is that dies are stacked up with many, MANY, more signals and channels. That's how NVIDIA has a memory bandwidth an order of magnitude higher than M4: 550GB/s for the M4 Max, 4.6TB/s for H200. And yes, that's bytes per second, not bits per second.
some GPUs use HBM. Most use GDDR. AMD and Nvidia still extract huge bandwidth from GDDR via high bus speeds + wide buses (like the 1.79 TB/s on the 5090)
CPU sockets with more than two memory channels are also far more expensive; the higher pin count usually increases the number of layers the motherboard needs, and the larger size of the socket requires more metal for stiffening (and EPYC CPUs still have issues with imperfect mounting leading to some IO lanes not working).
Using BGA soldering for both the processor and the memory sidesteps a bunch of engineering challenges.
by trading them with longevity challenges.
Even though 2 decades have past after the "usual suspect" lead-free solder, gpu or vram chips needing a reball is still a common occurrence from a cursory look at YouTube channels of professional electronics repairmen.