Economic mobility doesn't measure relative financial position either. Economic mobility only indicates position relative to a (highly variable) income distribution within a country. A "high" income mobility does not imply high relative changes in financial position, nor vice versa.

At the extreme, very small differences in relative income can make you "highly mobile" even though you've barely moved your relative financial position. This is seen in smaller industrialized countries with very compressed wage distributions. People in low mobility countries can have better financial outcomes in both relative and absolute terms depending on the mathematical distribution function, and do in practice.

The term "economic mobility" is widely used to push misleading narratives precisely because most people don't understand what it measures.