Although usually categorized as separate from blotting paper, differences in the constituents and thickness of blotting paper and watercolor paper are subtle, and making a distinction between the two is unnecessary as the production process is nearly identical.
While often considered separate from blotting paper, the distinctions between blotting paper and watercolor paper are minor, with their compositions and thicknesses being very similar.  Therefore, distinguishing between them is not necessary as their manufacturing methods are quite alike.