Blender 2.8-ADD Modiffier-Skin Modifier

Hello, I am a newbie user of Blender, I found a problem, I don’t know if it is a bug.
When I merge the plane Alt + M into the vertex, I add the SKin modifier to it, adding a level 2 subdivision. The 2.79 version is different from the 2.8 version. This makes me confused? I uploaded screenshots of the same version of the two versions for comparison.
Or maybe my operation is wrong?

Not sure if this is a bug or not, but if you Apply the Skin Modifier and enable display Normals, you will notice that the upper face is turned inside. The difference between 2.79 and 2.8 is that version 2.8 uses OpenSubdiv.