They should reduce the gain in the high frequencies for soft, loud, and MPO. Tell them you want to get them comfortable first, knowing you may sacrifice a little speech clarity (you can always go up again). Some fitters want to give you the biggest “wow” effect, by allowing you to hear a fly scratch his rear end from across the room. That often leads to people yanking them out and then what good are they? If costco gives you 90 days to try them, you don’t have to get it all at once in the first week.
Think of it this way, when you wake up in the morning and walk out into the kitchen where the sun is coming through the window, you squint. Why? Because you haven’t seen light for 6-8hrs. How long have you walked around with a loss before you decided to get aids? Few years if your like most people. It’s not fair to flip a switch and say “He’s all this sound, go home and enjoy it”. It can be overwhelming for some people!