Most dedicated GPUs have 2 or 3 monitor ports, so having the integrated GPU also support a extra monitor is not something that worked on windows (at least not u

Most dedicated GPUs have 2 or 3 monitor ports, so having the integrated GPU also support a extra monitor is not something that worked on windows (at least not until recently, I tried back in the day), also is not a something I would call a rough edge, let alone reasonable to expect in general.