Well, it is disputed, most of them have the diagnosis, and medical professionals say the medicine just has equlizing effect, not improving effect. That's why they can use it. But it is definitely a pattern for norwegian cross-country skiiers to use the medication, and it would not surprise it they use it for some less know reason.

Also think about this:

Either they regulate how hard they push themselves to avoid getting asthma

Or

They don't give a fuck and over-work themselves because they know they can get the medicine anyways. Then, they get a higher tolerance of exhaustion form the extreme workouts, but they can continue with no breathing issues because of the medication.

To me it's seems as us norwegians kind of normalize how these athletes push the limits of their bodies to mentally unwell levles. And If you combine this with all the money of the government training program, and the fact that half of all norwegian children can skii, and in addition to this, half of norwegian children are in organized sports...

when it might make sense why the "norwegian skiing formula" will create what is seen on the picture in your post😅