Offsetting the neoprene seal ends in their grooves simply insures that the seal ends are actually butted up to each other. If not offset, then the rear main cap (FE) or the seal housing (YBlk) can be mismatched just enough that the seal ends are not aligned with each other. Here’s the link to the comprehensive seal installation instructions.
http://www.eatonbalancing.com/blog/2008/09/10/neoprene-rear-seal-installation-for-the-y-and-others/