I guess it all comes down to experimentation. The circuit I posted is about as basic as it gets and I was aiming for the simplest solution based on measurements from my iPhone 3GS and Samsung S6 (around 1.5v) which both work with the Apple headset I got with my original 3G iPhone.
It looks like you've done somewhat more experimentation with those mics and I have no reason to doubt your findings and research. After all, the original Radio Shack PZM mics ran from a 1.5 volt battery but most of us who owned them (I still have two of them) pretty quickly found out that they ran fine on 12 volts and had better S/N and more headroom at that voltage. It's probably the same for the Apple headsets.
I was being cautious with my Apple headset recommendation because I didn't want to be responsible for providing a circuit that caused damage!
If you've ran them from higher voltages though, it's all good.