Dave, I think that the molding is simply filed into the sheet brass. I don't think it is bumped up or doubled, if that is what you might be thinking.
It is indeed odd that there is both a wood screw and a lateral pin hole for the back end of the trigger guard. I have not read the text that accompanies the pictures...do they mention this feature, and speculate upon the double attachment, as in, is this the original guard?