Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 425.31
Broken: version: 2.80 (sub 57), branch: blender2.7, commit date: 2019-04-17 19:26, hash: rBb46245470f79
Short description of error
There is a bug with Area stretch type in UV window. It doesn't show correct values (colors). Also it doesn't respect size of one object UV Islands according to another objects sizes.
[When you merge all object into one it all works! It doesn't work with multi edit.]
Exact steps for others to reproduce the error
2.Duplicate this cube, put it aside
3.Open first cube UV window
4.Move UV a bit that it doesn't overlap with other cube UV
5.Now select 2 cubes and open UV window, Go to Display>Stretch(tik)>Area
- Cubes UVs should be blue, now try resize one of them
They remain blue and they should changing colors based on size of the object and overall unwrap.
This bug is since forever in 2.80 and probably there's more realated to it.