I agree with your point, though I can easily modify ~/Library/Messages/Attachments or ~/Library/Containers/com.apple.MobileSMS/Data on macOS, which is a platform similarly secure to an iPhone when you take sandboxing, sip, etc. into account. So Apple already supports macOS, which can be tinkered, no? I guess the argument is that by locking down iOS, a platform which was never open, they just never needed to handle that class of security risks which are introduced when customers have more freedom.
I did actually discover a bug in iOS (related to photos which have failed to sync to icloud for the past four years) by investigating why there were over 23k empty folders in ~/Library/Containers/com.apple.photos.ImageConversionService/Data/tmp/, fwiw.
I did actually discover a bug in iOS (related to photos which have failed to sync to icloud for the past four years) by investigating why there were over 23k empty folders in ~/Library/Containers/com.apple.photos.ImageConversionService/Data/tmp/, fwiw.