Buzz, this isn’t meant for you to answer, simply to consider. The reason I am putting it forward is that it might give you a different take on space. Just consider this more like a Zen concept.
If the 4th dimension is just a measurement, why isn’t the 3rd just a measurement?
I think this discussion if continued would pull the thread off topic. Mainly I just tossed it out to see if it would give you a different way to think about space. If it doesn’t do that, that’s okay. Maybe someone else will have a comment that will help.