User blog comment:StonerCatJay/Rereading the series- theories and speculation/@comment-5551986-20140523175052

For the last part I don't think the short sword is a spirit weapon, just the fact that there was another thing similar to a soul inhabiting Ichigo's soul, and as such was created alongside Whites sword. Its hard to explain, even though its a filler arc, Shunsui had "two" spirits that composed his Zanpakuto, Ichigo could be the same instead of just banging to spirits into one blade it splits them in two, representing their separate identities in physical form.