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Where were you reading this? Apple devices do not “throttle” power sources (they are not chargers, they are a source of power). The charger is built into the phone, and takes whatever power it can safely use from the power source. In the case of an iPhone 14 Pro it will take 20W, regardless of the capacity of the power source. So it will take 20W from a 30W power source, or 20W from a 100W power source.
If the power source capacity is less than 20W it will take whatever the power source can provide. For example, it will take 10W from a 10W power source, or 7.5W from a 7.5W Qi wireless charger.
