This means that the new firmware will have more careful control over the processor and slow down its work under certain conditions. For example, if your battery capacity is below 80%, and you are either in the heat or in the cold. This is necessary to prevent the device from turning off unexpectedly.
In iPhone 11 and iPhone 11 Pro, the company has improved its built-in performance management algorithms, and processor slowdowns are not yet planned.
The iPhone XS and XR will get processor throttling feature with iOS 13.1 iOS 13.1 comes out next week with plenty of bug fixes. www.theverge.com