There is a difference. Gecko might implement features that would allow sites to work and look better in Firefox (for example, smoother scrolling, better animati

There is a difference. Gecko might implement features that would allow sites to work and look better in Firefox (for example, smoother scrolling, better animations, new CSS/HTML/JS features and so on). But Apple doesn't allow other browser engines, and Firefox cannot use this as an advantage to compete with Safari. Also, if Apple allowed other browser engines with better support for new features, then web developers might stop caring about supporting Safari. This might be another reason why Apple doesn't want other browsers on their devices.