the gp comment doesn't say that OCR is used. It says that the devices have the capability. Which is the case for recent iPhones : https://9to5mac.com/2021/06/10/how-iphone-live-text-ocr-work...

There is so much rich information in your photos, from memorable places you’ve visited to handwritten family recipes. iOS 15 uses secure on-device intelligence to help you discover more in your photos, quickly find what you’re looking for, and relive special moments.

My bad, I don't know how I missed that