Their AG is the determining factor for reciprocity. Regardless what their law says their AG has allowed states without an agreement to carry in DE including SC. He even states that the States listed to carry in DE doesn't recognize DE's permits. Delaware Department of Justice - Attorney Generals Office is DE's Reciprocity list and SC is on it. I'd have no problem carrying in DE. I'd just make a copy of their Reciprocity list and carry it with me while there.
However, as of today Delaware does not recognize the concealed deadly weapon licenses or permits issued by states other than those listed below, and these states do not recognize Delaware's concealed deadly weapons licenses as valid.