Yeah they do flower. Like all Echinodorus they produce long flower stems with whorls of flowers which are white petalled with yellow stamens. At each whorl they also usually produce some adventitious plantlets which will develop and grow roots and can then be detached and planted up. I have a half dozen or so little E.osiris 'Rubra' babies that came from the parent plant this way and my E.'Oriental' currently has a flower stem sticking out the back of the hood of my tank! No baby plants yet though, just flower buds.
I had to remove my 3 E.cordifolius from my old tank as they grew so large that they shaded the entire 180l tank so 12" isn't that big yet! Mine were producing leaves on 12" stems that were over 6" long! Would have been great growing emersed from the water on an open topped tank, but my tanks all have lids!