I don't know if the same 'rules' or custom applies to him but the 'thing', 'ritual' or 'rule' on burials in NOLA were once a body is intombed, the tomb cannot be opened for a year and a day. If another family member dies and they are supposed to be in the same tomb, their remains are placed in a 'rental' tomb on the wall of the cemetery. When the year and a day is up, they then moved the earlier burial remains to the back of the tomb and then brought the new one in. It seems someone had nothing to do so they figured out the rate of decomp in that climate and it then became the rule of thumb.
With the war on, even if the Confederate forces had still held NOLA, they may have intended to remove the body at a later date. Then again, with a war going on, all sorts of roadblocks come up to change and reshape the rule book.