Item X is imported with quanity 10 if inventory method in "Track Inventory" Item Y is not imported its inventory method is "Track Inventory With Product Attributes"
The plugin looks for the product. If the plugin can't find the product than the plugin looks for the product attribute combination.
>Although I suppose when inventory method = "Track By Product Attribute" the product SKU should be ignored I think you are right. I'll do the new release.