SH5 NEEDS Dynamic shadows

. Without dynamic shadows the realism factor goes down the toilet!
I've seen an SH5 trailer where in the engine room there were dynamic shadows cast onto the floor. I'm crossing my fingers. From other screen shots though it appears that there are no dynamic shadows.
I can't see how adding dynamic shadows results in major FPS hits. You have to add code to use the Stencil buffer which is relatively easy to enable you to make things like shadows and mirrors. C'mon devs, the game uses DirectX. DirectX makes it relatively simple to add mirrors and shadows to games. Enabling shadows involves some linear computations and all but it isn't drawing a complex 3D model so how is it an FPS hit? I'll give you that some blending might need to be done but this can be done via shaders (which is done on the video card's GPU) so once again how is this an FPS hit?
I haven't explored DirectX 10 but maybe that version adds some more functions that make shadows easier to do.
RB