https://www.cnet.com/news/mac-mini-2018-teardown-shows-swappable-storage-traded-for-memory-upgrades-ifixit/

iFixit's Mac Mini 2018 teardown reveals that Apple keeps its memory in a cage.

Another notable takeaway from the teardown: The service-center-upgradeable memory is encased in a cage. That explains how Apple was able to use faster 2,666MHz RAM in the small space without increased interference -- mini PCs usually incorporate slower memory. And the power supply increases from 85 watts to 150w in order to support the higher-power processor and port options.