It works on the same Chrome's engine even if you 'emulate' iPhone.
Google Chrome web-browser has an emulation mode, however, it basically resizes the viewport and emulates touch events. Nowadays we also need mobile browsers which don't exist on desktop machines. Several years ago, in a 'desktop era' it was enough to install all the web-browsers on the developer's machine and review a website in them.
Besides the adapted for mobile devices user interface, we also should ensure it works perfectly on a great variety of devices, screens, operation systems and web-browser engines.
This brings new challenges for web designers and engineers. Mobile first! It became true in the end of 2016 when a mobile web-browsing eventually overtook a desktop one. Victor Grinchik How to Install iOS Simulator and Android Emulator on Mac for testing and debugging your websites and webapps Introduction
