Question about the Eternal Contracts…

In this weeks chapter, we learned that the Eternal Contract the bearers have with the blades is a spell that uses the Shinuchi as the core to create all the other contracts.

But the Shinuchi is the 6th sword, made after the other 5.

Did the other blades not have a contract until the Shinuchi was made? Would that mean that until it was forged, the bearers also had their original sorcery alongside use of their blades?

Do you think this will be explained later or is it a retcon that horizontal forgor about?

In this weeks chapter, we learned that the Eternal Contract the bearers have with the blades is a spell that uses the Shinuchi as the core to create all the other contracts.

But the Shinuchi is the 6th sword, made after the other 5.

Did the other blades not have a contract until the Shinuchi was made? Would that mean that until it was forged, the bearers also had their original sorcery alongside use of their blades?

Do you think this will be explained later or is it a retcon that horizontal forgor about?