The problem with code breaking is that you can't benefit from it too much because your enemy will realise you're reading their messages and change their practices.
For this reason the allies had to let convoys be hit sometimes, because they couldn't always be too suspiciously at the right place at the right time. Luckily the German confidence in Enigma was so high that their top leaders ignored reports of enigma being broken, they thought it literally impossible.
I'm not sure how this played out in the Japanese war. But the point remains. You can't use signals intelligence too much unless it's literally ending the war in a couple of days.
For this reason the allies had to let convoys be hit sometimes, because they couldn't always be too suspiciously at the right place at the right time. Luckily the German confidence in Enigma was so high that their top leaders ignored reports of enigma being broken, they thought it literally impossible.
I'm not sure how this played out in the Japanese war. But the point remains. You can't use signals intelligence too much unless it's literally ending the war in a couple of days.