I think these aren't meant to be representative of arbitrary userland-workload LLM inferences, but rather the kinds of tasks macOS might spin up a background LLM inference for. Like the Apple Intelligence stuff, or Photos auto-tagging, etc. You wouldn't want the OS to ever be spinning up a model that uses 98% of RAM, so Apple probably considers themselves to have at most 50% of RAM as working headroom for any such workloads.