I have both Psoriasis and PsA so I may ask about it again.

Apparently it isn't FDA approved for Psoriasis (the company has tried)... but it has shown some efficacy in trials. It might be worth asking your doctor about, and they might be able to prescribe it "off label" (this may mean that your insurance won't cover it however).
If you don't have PsA but have a lot of the co-occurances that tend to go along with psoriasis (read: signs that the disease is active /inside/ your body), treating your disease like PsA might be worth it anyways. There is a small difference between the genes responsible but the disease process is widely the same regardless (immune response -> inflammation -> cell overgrowth)... so I have no idea why they act like it's different.

Best of luck!