Fascinating ancient textile--
Would love to have a look at that "seam" myself. Wonder if it's not a seam at all, but a fold in what very skilled weavers use in a process modern weavers called "double weave." This was how ancient weavers, not having wide looms, managed to weave wide cloth. You weave two layers at once, with a fold on one side and two selvages on the other. You have to string two warps, and keep both layers straight while wefting. Patience, skill, makes for a very expensive garment. The "veil" before the Ark was likely done with a variation of this process. It's written as being very heavy and thick, so I picture muliple warps and wefting most layers right together rather than layering.
Jesus's robe, a prize for the gamblers, is written to be "without seam." You can weave a pullover sleeved garment with no seam, if you know what you're doing.
I, for one, would hang on any word that a textile historian has to say. How accurate is carbon dating on an item less than ten thousand years old, anyway?