Most of them are for creating flanges for the supports (two right next to each other). The other ones are probably to make the supports look correct (beams going through beams, opposed to meeting strangely at one endpoint).
Not elementary or FVD. Those don't really produce an outrageous amount of vertices. Only AHG and Newton do. On the other hand, it's basically required that you run an elementary or FVD element through AHG before declaring it done, so I suppose that indirectly, yes, those do produce that many vertices...