Personally, I think it's like the synergy between the locks that enables them to seal Hwaran just because they can be rebuilt don't mean they will have that exact same synergy and even if they could it's only a temporary fix because what happens when MC's die of old age or something and there's no one able to do the same thing. The world is just left with this big bad evil guy no one can stop because the existence of the mc was the only thing protecting them.
Spoilers
But the person who replicates things has even the accuracy to replicate hwaran's aura without even meeting him in person so wouldn't he be able to replicate synergy that he can even reverse engineer since they've got the physical lock then it'd be easier with such a broken skill... just my thoughts though not sure if I missed anything or forgot something mentioned about a limit for it so I apologize in advance if I did.
When things have a multi placed "lock" for them why can't the people rebuild the one that's been destroyed before the other ones are destroyed? I mean, if they don't have the "tech" for it couldn't they reverse engineer the destroyed one and remake it...
(spoilers)
this one also has the advantage of having a guy that can recreate it with his power so idk why bother following the path of destruction when you could frustrate the heck out of them? ( • ⍨ •)