That doesn’t really mean anything. The explanation given seems to suffice It means other items in the coffin should have decomposed 100% as his body did and they didn't. It could mean his body was removed and is elsewhere. It means there are no relics of the newSaint... Deo gratias!
"Some preachers will keep silence about the truth, and others will trample it underfoot and deny it. Sanctity of life will be held in derision even by those who outwardly profess it, for in those days Our Lord Jesus Christ will send them not a true Pastor but a destroyer." St. Francis of Assisi