No, they're defined in the GtkBuilder .ui file as HildonButton with the properties "label", "visible" and "size" set: http://repo.or.cz/w/gpodder.git?a=bl.../fremantle#l62
Also, it looks fine in the SDK: http://khan.thpinfo.com/~thp/images/...ome_090616.png
Having a different theme/engine in the SDK and in the device (with major differences in rendering buttons, etc...) is really bad. Developers can test how things look in the SDK, but it's hard to find out what is wrong when not being able to test directly with the real theme. At least the theme *engine* should be the same in the SDK, if you don't want to publish the "final" theme (engine + colors, graphics, styles) right now.
Filed a bug report at https://bugs.maemo.org/show_bug.cgi?id=4710 I can't implement this, as the current theme on the devices seems to be different from the themes in the beta SDK, and I can't reproduce most of the UI/style/theme bugs you have here. Kind of an awkward situation :/