I personally think they should keep it this way because you can actually understand what she is saying.

In most episodes she doesn't have many lines so i think not having subtitles suits well. I think they only added subtitles in this episode because a lot of it was in Korean and the story may have not be well understood by some people if there were no subtitles. idk

They kind of needed to because nearly the whole episode was korean.

Simple, big lady centric episodes (must have subs). Minor appearances, no need for subs, make the audience wonder what she's saying without ruining the plot

I am Japanese Korean so ummmm, I say leave them Cuz then everyone can enjoy the "weird" things she says