It is a useless endeavor since Safari on Mac, iPad and iPhone all have different feature flags set and their own quirks related to how they are tied into system

It is a useless endeavor since Safari on Mac, iPad and iPhone all have different feature flags set and their own quirks related to how they are tied into system libraries on each platform. You would also not be able to test bugs related to interactions or the behavior of the GUI chrome. Browserstack is the closest solution to testing without being hands-on with a physical device.