A word for the property of scaling distance between two endpoints?
No, it's the wrong word. Scale applies to the domain. In your case, you want the opposite - your system is independent of scale. You want scale independence.
Example - http://www.vermontcomplexsystems.org/research/publications/unknown2016constrained
Constrained growth of complex scale-independent systems
Scale independence is a ubiquitous feature of complex systems that implies a highly skewed distribution of resources with no characteristic scale.