This is a common misconception; both were recommended because they performed equally well on available data at the time [1]. While CIELUV does have the advantag

This is a common misconception; both were recommended because they performed equally well on available data at the time [1]. While CIELUV does have the advantage that additive mixtures fall on straight lines in its chromaticity diagram, it does poorly at predicting color differences and has a flawed adaptation transform, so CIELAB is generally preferred. [1] https://doi.org/10.1002/col.5080150308 https://doi.org/10.1002/col.5080150308