Did you know that the cornstarch gel/paste can be used on sourdough and other. . .
breads to give a nice crunch, like you mentioned, seeds or not. The gel provides that gelatinizing effect that commercial ovens give with steam injection. I think I read it in Sunset mag.
Maybe you need to make the paste slightly thicker,, shape your loaves, brush it on, roll loaves in seeds then put in the pan? Or did you do this?