Source: Microsoft
Microsoft has brought its Xbox Cloud Gaming service to iOS back in June. But since it can only offer the service through Safari instead of a dedicated app, the experience isn't up to par with those on other platforms. And that's why Microsoft introduced a series of enhancements to improve overall performance for the iPhone and iPad. It optimized video output and network data transmission on iOS devices and found a way to reduce overall input lag. The latter will particularly be noticeable.
It seems to be the best workaround Microsoft can offer right now, short of releasing a dedicated app. The company is restricted by Apple's policies on game streaming apps, so it had to bring the service through the web browser.