How does the eye even "know" which kind of light it is? What's the difference, is one spectrum smoother and the other spiky or what? That's the part where a citation is needed.
Paper is more pleasant on the eyes for many reasons that don't apply to a reflective very bright projector screen.
This is me being a 100% armchair physicist, but I'd theorize it'd be something like trying to iluminate a room with a flashlight vs pointing it to a white (diffusive?) surface, counter intutively you achieve better* ilumination with the aditional diffusive surface
Paper is more pleasant on the eyes for many reasons that don't apply to a reflective very bright projector screen.