That's for the base model M6. The Pro can take more, the Max even more, the Ultra the most.

They're not making those models for the M6 though; they rerouted their resources to making M7 faster at running local LLMs.

If you want more bandwidth, get an M5 Pro, Max, or Ultra. If you want a lower power base model, get the M6. If you want to have your cake and eat it too, wait for the M7, reportedly in the spring.

Umm yes, the M6 chip only has a certain amount of memory controllers and channels, which means you can only have so many LPDDR5X modules.

Yes, high-capacity LPDDR5X are made and do exist, but for all practical intents and purposes, you can't buy enough of them to deliver to customers at Apple scale.