One should be at the bottom one at the top. I understand space on the phone is a premium but a second port would make the phone so much more usable. Wired headphones, flash drives, camera modules, speaker modules, keyboards, even connection to a TV, all could be used while charging. It’s a shame it’s not a thing, USB is extremely versatile port, but you only get one and it’s used for charging half of the time. (I am aware dongles exist)
Not sure what exactly you mean by headset. But headphones and IEMs will use a 3.5mm or 1/4" jack. My sennheisers use it, my beyerdynamics use it, my audio Technicas use it. Even my KZ IEMs and moondrop IEMs use it. This is a universal standard for a reason.
And not sure what the data rate has to do with anything. It’s an audio connector, it’s not used to transfer data, it’s used to move the drivers in a set of headphones. As usb-c doesn’t output line level audio, any headset you have that uses it needs its own DAC and amp which is problematic for e-waste reasons.
Headset, as in headphones with a microphone. I use it for MS Teams meetings and a bit of music and it works fine.
The point OP was trying to make is that you can use USB-c for other things besides listening to music.
Since you seem to be an audiophile with a list of fancy headphones (don’t ask me, my Cardo combined with earplugs is fine for the level of listening I want to do) then wouldn’t an offboard DAC / amp that you could keep far longer than a phone, and isn’t restricted by size constraints going to be better than a built-in version?
Also, if you’re worried about e-waste maybe you shouldn’t buy so many headphones. My partner’s Sennheisers have lasted 20 years so far.