The examples which you brought up as a counterpoint to Immeasurable Speed existing all have explicit in-universe factors that allow them to travel through time and differ them from the actual definition of Immeasurable, stuff like Superman time traveling by moving faster than the Earth's rotation and what have you, so they are not really applicable as examples here, especially since, like I said, Time Travel is a subset of Immeasurable Speed, and not the main idea behind it.
And that's not even to bring up how you can still qualify for it in other ways, like what I've mentioned in the very same post which you are addressing.