The mic has a given operating range. Believe it or not mics can withstand explosive decompression.
Below 25dB is irrelevant as the mic noise floor is about this, inputs over 110dB are also irrelevant to speech as the aid isn’t going to do anything with them. That gives you 85dB dynamic range, chop it up as you want.
There will be a calibrated level of sensitivity and a phase angle, why would you be introducing distortion under normal operating conditions. It’s not designed to add anything to the signal.