It was never going to cause cancer anyway. The limits in France are just really low. Phone radiation is non-ionising, which at the levels it emits is harmless, even the one that breached France’s limits.

No, cpu and antenna power aren’t the same thing.

It's not ionizing. It'd be impressive (and probably highly illegal) if it was. The "radiation" was below the range of visible light (technically, visible light is a form of radiation), meaning it's fairly low energy. In order for it to increase your cancer risk, it needs to be above the visible light spectrum (ultraviolet and higher), otherwise it lacks the energy to damage cells directly. Their use of the term "radiation" is hard-core clickbait.

Radiowaves, microwaves, infrared, visible light, ultraviolet and x-rays are all radiation, and they're all light. If you had the right tools, you could theoretically take a picture using only microwaves and/or radiowaves. Additionally, radiowaves and microwaves are below the visible light range (so they don't cause cancer) and require a ton of power to cook something (microwave ovens are usually +1000 watts, iirc the iPhone was putting out slightly more than 5 watts in the radiowave range, which afaik requires more power to cook something).

No this will likely limit the max antenna range and give you worse radio reception, but will make no difference to the CPU that runs the UI and apps

There's an option to disable the underclocking in the battery section. Here's an Apple Support article on it. It's under the "Performance management turned off" heading. You could have the battery serviced.

I'm impressed your 12 has gone that far already, my XS hasn't gone that far and is still on the original battery.

They could have found a fault in power delivery, which could be the issue. They may just be correcting it. You can guarantee there will be back to back tests done to show any difference, so time will tell.