@JohnPhilpin A critical component of all web browsers is the browser engine. That's the part responsible for rendering the actual webpage, turning HTML code into text, images, buttons, and so on. For example, Firefox uses the Gecko engine, while Chrome and Edge both use Blink.
On iOS, the only browser engine allowed is WebKit (which powers Safari). So when you install, for example, Firefox on your iOS device, you won't get Firefox with the Gecko engine; you get Firefox with the WebKit engine. Or, if you will, you get Safari with a different skin.
So even if it looks like you have a choice of browser on iOS, you really don't. At least not when it comes to the engine. The core part is always WebKit – which Apple controls.