Broken: 2.79. 2.8*
Importantly for games with Weighted Normals and Bevels workflow it would be very desirable for Corners of UV to scale and connect correctly so there are minimal distortions and UV disconnections.
This is how it opens in max post export:
Please also note that in 2.8 Bevel modifier completely distorts UVs in "Vertex average"(and possibly other) Normal Modes. Works as in 2.79 without any normal mode.
Prepared debug scene (as requested by Howard):
Also available here: http://cgstrive.com/blend/debug_bevel_uv.blend