Agree. Though, I think they are making a distinction between the Hindi 1. ...में द्रद है। There is pain in ... 2. ... में दर्द हो रहा है। ... is aching.
This is why it's inconsistent between those two variants.
In English we use the two formsv also slightly different, e.g. My muscle had been aching all day (though this is perfect if there continuous) as opposed to: I have pain in my arm now (but not before).
Though the also accepted: I've am headache (can't remember, but i think for nr1).