It puts the Japanese in a bind to protect Korea from American hands and pulls the IJN north. I could see it being used situationally, but I don’t know if it’s something I’d do all the time. If Japan’s strong enough, they could have a strong enough fleet to stop your USN and still make headway in the $$$ islands. Don’t forget Japan will have their kamikazes and they could easily plop an airbase on korea to scramble 3 more fighters, & any builds will be available right then to stop your advance. They can send a small fleet against the $$$ islands and still have the strength to fend you off.
You limit your options and remove the USN presence down south where it might be needed. IMO, if you’re going to build a naval base why not put it on wake/midway? They already have airbases that you can use, they are both a turn away from reinforcements, and Midway can still reach the same territories + both give you more options. I typically don’t build naval bases in the pacific with US, but I prefer Midway when I do since it gives you more routes to Japan and it’s harder for Japan to block counters if he does sail against you.