I remember discovering this the day of the no-sheath patch when i accidentally produced like 25 masterwork Long spears. My team all grabbed one. It was siege defense. We won.
They are already aware of it to my knowledge. It is just one of those weird things that happens with "Can't be used on horseback" conflicting with "Can not be sheathed". Sometimes you can use the long spear while on horse back too! That was the bug I was trying to replicate just for giggles.
