There's still things that are impossible to accurately measure from within our reality.

We, for instance, can't know or measure the precise state of things as they would've been had something different occured than what actually occured at an earlier time.

This is especially obvious in the realm of quantum mechanics, where you can't know what you would have measured if you had measured earlier or later than you did (I hope my interpretation as a layperson was correct here). That information just doesn't exist in our reality, but it may exist in some higher order place where all those realities can be observed.