Why do you assume that it is a design choice when it is far more likely a bug?
Why do you think it is a bug? Some battles are scripted (like the Doctor for example).
I found this one terribly hard first playthrough and had to run away but second time (when I was badly overlevelled) it was trivial.
Seems more like trying to fight someone at the wrong level to me in which case (like elsewhere) buggering off and coming back later seems a decent strategy.
