Should a patient on medium-dose ICS/LABA with normal PFTs, but who shows a greater than 10% decrease in FEV1 if their PFTs are done after 24 hours off their inhaler, be started on a biologic?

A little more clinical information would be useful to better answer the question. How well controlled is the patient on the LABA/ICS? What is the ACT score? The FEV1 decreased by greater than 10% (with volume >200 ml?) when LABA/ICS was stopped for 24 hours - how quickly did it normalize when the inhaler was restarted? As for the FEV1 changes representing continued mucosal inflammation that would ultimately lead to progressive scarring, I think it is premature to say that definitively since it is unlikely that the biological effect of an ICS would be so short-lived in a patient with normal spirometry just 24 hrs. before to decrease FEV1 because of airway inflammation. If this were true, it would imply that regularly using LABA/ICS is only "...

Thank you to Dr. @Dr. First Last for his answer. To add some information, the patient is asymptomatic and not needed a steroid burst for respiratory infections. Their FEV1/FVC also drops if spirometry is done when they are off their inhaler for 24 hours. Also, if they miss a dose or two of their inhaler, they feel they need albuterol. It seems to me that the ICS dose is not fully eliminating the underlying inflammation. Since we know that the benefit of increasing the ICS dose above the current 160 mcg, 2 puffs twice a day of budesonide is likely to be limited, I wonder if it would be worth doing an eosinophil count. If it were over 300, perhaps an empirical trial of a biologic would be worthwhile?