That argument is what really made me fairly sure it’s not His shroud. I don’t know what it is (I’m not convinced it was painted, seems like it would have been difficult to paint, especially way back). But it doesn’t fit the description in the Bible, or apparently, the practices of 1st century Jews.
I have no idea who made the shroud but I can’t see reading into the Gospel’s what isn’t there in order to make a foundation for the Shroud.