The examples display a degree of vorticity that I have never seen in real life watercoloring. They look great superficially, but they look super weird at reasonable inspection. Water on paper does not flow nearly so freely.
That said though, lovely site and project!
Whatever may be important to you, the website clearly presents itself as trying to realistically represent watercolor. It's a fine-ish first order approximation if you squint real hard, but doesn't capture the dynamics of watercolor.