Yes, Kallista, if you use the medium, the paint does dry very glossy. But the same will happen with traditional oils if you use the classic old master mixture of 1/3 turp, 1/3 linseed oil, and 1/3 damar varnish, which is what I learned in art school.
I'm going to experiment with my next water-mixable painting: laying down the first layer with no medium, then letting it dry and adding a colored glaze over top with medium.
There are many different ways of painting with oils. I usually paint alla prima because I'm too impatient to wait for something to dry, but the other way of painting (the old masters' way) produces some interesting effects too.