iPhone irrationally adjust media volume when playing system sounds through connected wireless headphones

Currently using iPhone 13 Pro, also replicable on iPhone 13, both iOS 16.5.1, bug exists before latest update. Headphones used is Sony WH-1000XM5 (on firmware 1.1.3).

For some context, if it helps, I keep my media volume around 25~30%, and my ringtone volume at 50%. I have lock screen sound and keyboard typing sound turned on. This issue only happens when your ringer is not muted.

To replicate the issue, connect the headphones to the phone. Do not play any media (music for example). Try to make the phone play system sounds through the headphones (e.g., Lock Screen, battery charging sound). Then resume to play your media, you'll be greeted by a sudden volume change of your media to at least 50% or higher, sometimes 100% even.

I can confidently say that this issue is on iPhone only since I never met this issue on my MacBook Pro till this date.

This has been a hearing hazard to me, as it happens without notice and suddenly. This makes me hate iPhone now, it has brought me a worse experience and was causing trouble for my experience with my new pair of headphones too.