I think this is not so much a bug as a feature of sorts. I think the base problem is that at least Inkscape (because thats all I've used) doesn't snap the objects in a group to the grid. It does (apparently whenever it feels like it) add translation and scaling I think making things even less correct. Some of the foot prints I've seen aren't actually on .1 centers but rather .104576 etc (and different between pins) not enough to bother anything too much in the real world but not correct as it could be either. The solution in my head (which hasn't yet made it out my fingers, because I'm still unscrewing my previous errors in parts creation 
) is a prototype footprint editor in perl/tk that would do only the stuff needed to make footprints not all the general stuff that Inkscape supports. Tell you what the pad and hole size of this pad is, align it to the grid exactly (unless you tell it not to), Repeat this same pad .1 (or whatever) spaced horizontally or vertically. I think that is what the developers originally intended with the next version of the parts editor. Perhaps I'll get there first, perhaps they will 
. As to the group, parts-help seems appropriate to me as this is likely really about the parts.
Peter Van Epp