Yes. I have celiac disease and have had no problems with this product.

Does anyone know why the label has a reproductive harm warning on it (p65 ca warning)?

I have a couple of these in my curry spice collection. Mine has no warning, but I can see yours has 3 paragraphs on the left where mine only has 2 + a UPC bar code. Maybe different ingredients? Mine lists, in order of quantity: Turmeric, Coriander, Fenugreek, Cumin, Orange Peel, Pepper, Chili Pepper, Cinnamon, Fennel, Ginger, Star Anise, Thyme, Bayleaves, Cloves, Nutmeg, Sage and Cardamom. . .all great stuff. Let me know what's different in yours if anything. I'm 72 so I'm not concerned about my 'reproductive' health 🙃 😁 Lin

Is this really the yellow and red can variety? (the all red IS different flav wise)?

I assume they are different but red and yellow is pretty mild. Need to use a lot to get flavor.

Aside from being a powder, how is this different from the blocks of S&B curry sauce?

Taste-wise, there seems to be no difference. Curry sauce blocks are just roux (with moisture removed? I'm not sure), so I'm assuming in addition to the powder, the blocks also contain fat and flour. The powder is just the third component of the blocks - the spices.