It's just that pilots have no capacity left to be fluent in every languages everywhere. You don't avoid ambiguity speaking in the second language in a critical situation, you just incur significant responsiveness plus bandwidth penalty.

There are few recordings of aircraft emergencies over Japan on YouTube. Two obvious things in those recordings are that local pilots drop pretense of speaking Engurish in almost any non-normal conditions, and that local ATCs are dangerously useless outside of normal conditions. There's nothing visibly helpful from using English in there.