Tubular woven linen?

I found some nice, old linen pillow cases at Goodwill recently with filet crochet lace trim inserted by hand, and obvious machine stitching on the seam. The thing I’m having trouble finding out more about it the manufacturing process that made the linen.

It’s tubular. I can see areas that are similar to a selvedge edge, but there are no seams on the case except to close it at the end. The “selvedge” portions just continue back into the normal weave with no seams like a modern T-shirt without side seams.

I can’t find any information on this process, all my searches for “tubular woven fabric” turn up info about knits or specialty industrial fabrics.

I’m interested in textile history so I got curious and though maybe the folks in this sub would know where to point me. Thanks!