i also think it's a sakiori
to does this sort of japanese weave stuff as his project, and he knows a ton of stuff re: japanese vintage and textiles. maybe you can send him a DM asking
he referred to this one as a "sakiori", so i'm inclined to believe its a very tight weave sakiori but i'm no expert. i think it's also possible it might be a rough tateyokogasuri where the warp and weft are dyed with natural color variation and woven without a pattern, but idk