I am sorry but I find it hard to believe you.
I have tested at least 16 new iPhones (iPhone 12 and iPhone13 models) in Apple store and Malls.
All of them had the same problem.
Then I have tested all my friends and family iPhones (several 8, 10, XR)…same problem.
You are the only one blessed with Loud Alerts Volume iPhone.
Can you swear that you performed my test correctly and confirm that setting the same “Sonar” sound to both Text Tone and Ringtone, they both have equally loud volume?
Please, if you can and if you want, make a video and post it here or YouTube and show us your Alert Volume working iPhone.
If you’re willing to do it, please do not use the iPhone screen recorder because the internal audio compression normalizes all volumes to the same level and it is impossible to tell the difference. Just use another phone brand to make the video.
Anyway, I am not insinuating that you are a liar, I just think that something is wrong and if you felt that way or your iPhone really works properly, I’ll give my apology.