I am not an expert, but here's my guess:
Every Aspie is different. Some think visually and don't have NLD. Others have NLD and can't think visually. It just so happens that both visual thinking and NLD has a high occurance with AS. It doesn't necessairly mean a person has both. Like how a lot of Aspies are a maths genius, but there are also a lot of Aspies who struggle with it.
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Life ... that's what leaves the mess. Mad people everywhere.