Dam, just typed a reply then lost it. Here comes the short version:

Sail cloth is made on a machine like this to a layout as designed by your sailmaker, then sent to them to broad seam and detail. So yes despite the apparence in the photo, the threads are broken at the seams.

Given my main was made in Landy's German loft, it is probably safe to say the material was made by Dimension-Polyant, but I thought he mentioned something being done in Italy.