iPhone 15 Music fade-in cannot be turned off.

Title. I spent 40 minutes with the people who sold me the phone (the local Verizon), and we could not find an answer.

A summary of all that I can remember about our interaction:

--bluetooth headphone users are experiencing the same problem, so it's not my headphones or the adapter (which are Koss over-ear-loop 3.5mm with a USB-C adapter).

--I deleted the Health app, because somewhere in the phone settings it says that headphones follow the Health app settings.

--I unplugged the headphones, went into Settings and told the phone to forget all USB history; plugged it back in and hit "other device" instead of "headphones" (to try to get the phone to think it's not headphones so as to not auto-mess with the settings.). Didn't work.

--I'm not streaming anything; all of my audio is on-device; in any case, I disabled Music from accessing cellular data. 



None of this worked.

Note: the problem does *not* happen over Bluetooth when interfacing with my infotainment system in my car.

--my iPhone SE 2022 does *not* have this problem.

Nothing to do with the Crossfade setting. That is turned off anyway. Nothing to do with the Reduce Loud Audio setting. That's turned off anyway.

Is this a "feature" that I can't turn off? I have yet to physically go to an Apple Store because I just got home from Verizon, but that's next on the list once I can physically and mentally do it.