Broken: 2.80 (sub 47), a0f2923fd821, 2019-03-08 21:52
Short description of error
The problem is on the picture.
Perhaps it caused by arithmetic mean or another wrong function for color calculation: so three vertices, that not distorted are affects much more then one hardly displaced.
Perhaps it should count area or difference between edge-length and difference between angles on the geometry and on the UV.
IDK if it is bug or wrong choice of function, but it is obvious, that such map do not show actual problem with red.