It all depends on the person. I have never had any trouble inhaling 7% saline. The first time, I coughed a bit while inhaling, but that was the extent. It doesn't feel uncomfortable.

So did they explain why? Or prescribe it? I have hyper-reactive airways, and it doesn't give me any problem.
Funny story though. We went on a short trip and I left my nebulizer home. Last neb was Friday morning. Sunday afternoon I got a coughing spell. The mucus that came up still tasted salty! So it sits in there and bathes the tissues...
You might want to refer them to the following link from National Jewish Health, which lists 7%saline as part of the airway health routine.
https://www.nationaljewish.org/NJH/media/ProEd/NTM%20Provider%202019/McShane-Bronchiectasis-NEW.pdf
Sue

Some of us cannot tolerate 7% or even 3%. I was started on 7% when I was first diagnosed with bronchiectasis in 2011. I used it twice a day for years without any problem. But eventually I could not use it. I would inhale nebulized 7% and immediately start coughing. After 5-10 minutes the coughing would finally slow and I would try inhaling the 7% again but the coughing would start again. I had to stop using it.

When I changed pulmonologists in 2018, my new doctor prescribed 3%. Although I coughed a lot I was able to use it for a year or two but then the bad coughing started right after the first inhale and continued just like the 7% and I stopped.
Last year, Dr McShane who has treated my bronchiectasis. MAC and other organisms, sent me an article about the efficacy of .9% in moving sputum out and I have been able to use it.

I believe that I have trouble with saline because I have a lot of inflammation. I have chronic bronchitis in addition to bronchiectasis and my lungs are very fragile and absolutely do not want any salt on them.

We are all different and you may be ok with 7%. If not maybe you can use 3%. But if your lungs will not tolerate either of these, then .9% will help get the sputum out although it will not kill any bacteria.