Question: someone might ask is why doesn't it say this in lisanularab in more specific terms?
However what is interesting is that lisanualarb does mention the following entry to support the argument that I am making. It says:
أَراد بالنطفتين بحر الروم وبحر الصين لأَن كل نطفة غير الأُخرى
"The meaning he intended with Al-nufatayn ( The 2 nuftahs i.e the dual of nutfah) is with the roman sea and the Chinese sea because each nutfah (sea) is different from the other."