documentation for TextureImporter is vague on max texture size

http://docs.unity3d.com/Manual/class-TextureImporter.html
"Note that each platform may impose maximum texture sizes."
I would like to see a breakdown of this, per platform.

For example Unity recently exposed 8k textures (for DX10-ready hardware & up from googling), but DX11 supports 16k textures: if I switch my project to DX11, will it be enabled?... no idea.