From the link you provide
- Bluetooth uses no energy unless it is connected to a device.
Mine is connected to hearing aids all the time.
- that still means that if your battery life isn't what you think it should be, the problem is not Bluetooth or Wi-Fi.
Was referring to an iPhone 8. Mine is a SE gen 1, and the battery is about 83% health.
I don't really use my phone for anything other than controlling hearing aids. I make 2 calls per month. I send 2 texts. I rarely use it to browse. Still, since getting the hearing aids (I never had bluetooth activated before) if I forget to plug it in at night then it's at 1% power the next morning.