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The resources could have been left as they were. I don't understand this move.
The goal of renaming is to align the resource names with the realities of Ashan.
In previous installments, the resources for construction were chosen, one might say, randomly. In any case, I don't know why gems are necessarily needed to hire minotaurs, and mercury is needed for nagas.
In the seventh installment, there will obviously be a more logical justification. For example, twilight steel is needed to produce constructs from twilight steel, star silver is needed for blade dancers, which is used to make their blades, and magical crystals are needed to summon spirits (ghosts, djinns, dryads), and so on.
This will create not only greater realism but also make it easier to remember the required resources, as it will create more logical associations.
At least, I hope that is the reason.