The other 150,000 were free to continue roaming around.
Following the bombing of Pearl Harbor, US Territory Hawaii was assigned a military governor and placed under strict Martial Law. Considering Hawaii is a cluster of islands, I’d say the imposition of curfews, and limits on island-to-island travel was a pretty equivalent lockdown for a island population that was at least one-third Japanese. And, it was much more logical than relocating that large of a population to the mainland. The key phrase is “US Territory”